BOTANICAL  DEPARTMENT 


IOWA  STATE 
COLLEGE 
of 

AGRICULTURAL 

and 

MECHANIC  ARTS 
No.  35. 


CONTRIBUTIONS 


FROM  PROCEEDINGS  IOWA 
ACADEMY  OF  SCIENCE, 
VOLUME  XIV. 


CONTRIBUTIONS 


BOTANICAL  DEPARTMENT 
Iowa  State  College 

OF 

Agricultural  and  Mechanic  Arts 


No.  35 


From  Proceedings  Iowa  Academy  of  Science 


VOL.  XIV. 


S>0 


IOWA  ERYSIPHACEAE. 


BY  J.  P.  ANDERSON. 


INTRODUCTION. 


The  Erysiphacese  are  popularly  known  as  blights,  white  or 
powdery  mildews.  They  are  parasitic  on  quite  a large  variety  of 
plants  and  during  the  summer  are  often  quite  conspicuous  factors 
of  the  vegetation,  covering  the  leaves  or  other  parts  with  a white 
mycelium  which  sometimes  gives  the  host  an  almost  hoary  ap- 
pearance. 

The  plant  body  proper  consists  of  numerous  branching,  septate, 
usually  white,  much  interwoven  threads  called  the  mycelium.  These 
threads  are  superficial  and  adhere  to  and  derive  nutriment  from 
the  host  by  means  of  haustoria  which  arise  from  the  mycelial 
threads  and  penetrate  the  epidermis  of  the  host.  An  exception  to 
this  is  found  in  Phyllactinia  in  which  special  branches  of  the  my- 
celium enter  the  stomata  of  the  host  and  send  haustoria  into  the 
surrounding  cells. 

During  the  summer  and  early  fall  the  asexual  reproductive  bodies 
or  conidia  are  formed.  They  are  cylindrical,  oval  or  barrel-haped, 
colorless  cells  filled  with  protoplasm.  They  are  formed  by  constric- 
tion at  the  ends  of  short,  erect,  simple,  club-shaped,  septate,  color- 
less branches  of  the  mycelium  known  as  fertile  hyphse  or  conidio- 
phores.  The  conidia  are  often  found  in  chains,  several  from  the  end 
of  the  same  hypha  having  fallen  away  together.  The  conidia  are 
produced  in  immense  numbers  throughout  the  growing  season,  are 
light  and  easily  carried  by  the  wind,  and  serve  for  the  rapid  increase 
and  wide  distribution  of  the  parasite  as  they  germinate  quickly 
under  favorable  conditions.  In  germinating  the  conidium  sends 
out  a slender  tube  which  upon  the  proper  host  and  under  the  proper 
conditions,  soon  develops  into  a new  mycelium. 

Later  in  summer  or  in  autumn  the  true  reproductive  bodies  or 
perithecia  are  formed.  These  perithecia  contain  the  ascopores  or 

P 40151 


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resting  spores  whose  function  seems  to  be  to  carry  the  fungus  over 
from  year  to  year. 

The  development  of  the  perithecium  is  as  follows : At  the  point 
where  two  hyphse  cross,  or  at  the  place  where  two  neighboring 
hyphse  touch  each  develops  a small  upright  branch  which  is  soon 
separated  from  the  parent  hypha  by  a partition.  One  of  these 
branches  swells  into  an  oval  shape  and  becomes  the  carpogonium. 
The  other  elongates  and  applies  itself  closely  to  the, carpogonium, 
curving  above  so  that  its  end  lies  on  the  apex  of  the  carpogonium. 
The  upper  part  is  then  cut  off  by  a septum  and  forms  the  antherid- 
ium.  At  the  time  of  fertilization  the  wall  between  the  two  organs 
dissolves  and  the  nucleus  of  the  antheridium  passes  over  and  unites 
with  nucleus  of  the  carpogonium.  A new  wall  is  afterwards  formed 
between  the  two  organs. 

The  development  of  the  walls  of  the  future  perithecium  begins 
when  the  two  nuclei  unite.  From  the  stalk  cell  of  the  carpogonium 
a number  of  hyphal  branches  grow  upward  forming  a single  layer 
around  the  carpogonium.  Later  the  stalk  cell  swells  and  a second 
series  internal  to  the  first  grow  up  in  a similar  manner. 

When  the  perithecia  are  about  half  grown  certain  cells  of  the 
outer  wall  begin  to  grow  out  into  appendages.  These  cells  are  situ- 
ated either  apically,  equatorially,  or  basally.  These  appendages 
vary  in  character  and  with  the  number  of  asci  form  the  character  on 
which  the  genera  are  based.  They  are  probably  concerned  with  the 
distribution  of  the  perithecia. 

The  perithecia  when  mature  vary  from  globose  to  cup-shaped  or 
pezzoid.  They  are  generally  blobose-depressed.  The  perithecia  con- 
tain one  to  many  asci  each  ascus  containing  two  to  eight  colorless 
spores. 

With  the  formation  of  the  perithecia  the  mycelium  sometimes 
completely  disappears.  Frequently,  however,  it  is  persistent.  • 

The  asci  are  liberated  by  the  irregular  rupture  of  the  wall  of  the 
perithecium.  The  ascospores  seem  incapable  of  germination  before 
passing  through  a resting  stage.  In  a damp  atmosphere  or  water 
they  send  out  germ  tubes,  which  on  the  epidermis  of  a suitable  host 
plant  penetrate  and  form  a haustorium  from  which  center  the  or- 
dinary vegetative  mycelium  is  produced. 

Economically  the  Erysiphacese  are  very  important.  They  injure 
many  species  of  cultivated  and  native  plants.  As  examples  we 
need  only  cite  the  mildews  infecting  the  grape,  gooseberry,  rose, 
cherry,  plum,  apple,  and  various  forest  and  ornamental  trees.  They 
work  injury  by  impairing  the  function  of  the  leaf  and  causing  a 


5 


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J 


premature  dropping.  Frequently  other  soft  parts  are  also  attacked 
which  renders  the  injury  to  the  host  much  greater.  The  loss  to 
farmers  and  horticulturists  through  this  source  is  often  much 
greater  than  is  at  first  apparent.  The  weakening  of  the  vitality 
of  the  plant  brings  a less  abundant  harvest. 

The  choice  of  hosts  by  the  various  species  of  Erysiphaceae  is 
varied.  Somey  e.  g.  Uncinula  geniculata  on  Morus  rubra , are  con- 
fined to  one  host  plant.  Others,  e.  g.  Uncinula  circinata  on  species 
of  Acer,  are  confined  to  a single  genus.  Still  others,  e.  g.  Uncinula 
salicis  on  Salicacese,  are  confined  to  one  family.  Lastly,  some  grow 
on  a great  variety  of  host,  plants,  e.  g.  Erysiphe  polygoni. 

Sometimes  perithecia,  when  crushed,  instead  of  emitting  the  us- 
ual asci  emit  a stream  of  small  oblong  spores  6.5 — 10.5x3.5 — 6 
micra  immersed  in  a colorless  gelatinous  substance.  In  such  cases 
smaller  bodies  oval  to  pyriform  in  shape  will  also  be  found.  These 
rupture  irregularly  and  emit  the  same  kind  of  spores.  Often  these 
bodies  are  found  where  no  perithecia  have  formed.  They  belong 
to  a plant  parasitic  on  the  mildew.  By  careful  examination  the 
delicate  hyphae  of  the  parasite  may  be  seen  within  the  hyphae  of 
the  mildew.  If  the  mildew  attacked  is  in  the  perithecial  stage 
the  perithecium  is  filled  with  its  fruits.  If  the  mildew  is  in  the 
conidial  stage  the  attack  of  the  parasite  seems  to  prevent  the  for- 
mation of  perithecia  but  the  fruits  of  the  parasite  are  often  found 
in  abundance.  This  parasite  is  Ampelomyces  quisqualis  Caseti. 
(See  plate  I.)  It  undoubtedly  serves  to  hold  the  mildew  in  check. 
It  seems  to  attack  all  species  of  Erysiphaceae.  During  the  past 
two  years  it  has  been  abundant  in  Decatur  County,  infesting  the 
mildews  on  the  following  hosts: 

Aster  cordifolius  L. 

Aster  laevis  L. 

Aster  multiflorus  Ait. 

Aster  salicifolius  Lam. 

Adicea  pumila  (L)  Raf. 

Ambrosia  trifida  integrifolia  (Muhl.)  T.  & G. 

Carduus  altissimus  L. 

Cucumis  sativa  L. 

Hydrophyllum  virginicum. 

Lactuca  canadensis  L. 

Lactuca  fioridana  (L.)  Gaertner. 

Lactuca  sagittifolis  Ell. 

Monarda  fistulosa  L. 

Physalis  heterophylla  Nus. 


6 


Rosa  sp. 

Rudbeckia  laciniata  L. 

Solidago  canadensis  L. 

Verbena  urticifolia  L. 

In  some  cases,  e.  g.  on  the  species  of  Lactuca,  every  specimen 
collected  and  examined  proved  to  be  infested  by  the  Ampelomyces 
while  in  other  instances,  e.  g.  Verbena  urticifolia  only  an  occasional 
specimen  was  found. 

Often  conidia  bearing  mycelium  is  found  on  a host  and  no  peri- 
thecia  are  formed.  In  Decatur  County  I have  found  conidia  on  the 
following  hosts  not  reported  under  any  species  in  this  work.  In 
the  absence  of  perithecia  it  is  impossible  to  definitely  determine 
the  species  to  which  they  belong: 

Asclepias  tuber osa  L. 

Aster  multiftorus  Ait. 

Brassica  sp.  (Turnip.) 

Cucumis  sativa  L. 

Dio  spy  r os  virginianum  L: 

Geum  virginicum  L. 

Lactuca  canadensis  L. 

Lactuca  floridana  (L.)  Gaertn. 

Lactuca  sagittifolia  Ell. 

Monarda  fistulosa  L. 

Physalis  heterophylla  Nus. 

Potentilla  monspeliensis  L. 

Rudbeckia  laciniata  L. 

Rudbeckia  triloba  L. 

Solanum  carolinese  L. 

Solidago  ulmifolia. 

Xanthium  canadense  Mill. 

To  these  should  be  added  the  following  reported  by  Prof.  Fink 
at  Fayette  in  1893 : 

Chrysanthemum  sp.  (Curt.) 

Grindelia  squarrosa  (Pursh)  Dunal. 

Mesadenia  tuberosa  (Nutt.)  Britt. 

Phlox  sp. 

Physostegia  virginiana  (L.)  Benth. 

Roupa  sylvestris  (L.)  Bess. 

Sisymbrium  officinale  Scop. 

On  the  same  host  plant  perithecia  may  be  formed  one  season  but 
not  another.  During  1904  I looked  for  perithecia  on  Verbena 
hastata  and  V.  urticifolia  but  found  none  although  nearly  every 
plant  of  the  hosts  were  more  or  less  affected  with  the  conidial 


7 


stage  of  E.  cichoracearum.  In  1905  I found  perithecia  in  abundance 
on  both  hosts. 

The  data  contained  in  this  paper  are  mainly  the  result  of  two 
years'  observation  on  the  family  in  Decatur  County,  together  with 
an  examination  of  the  collections  at  the  Iowa  State  College  at 
Ames  and  the  State  University  at  Iowa  City.  The  herbarium  of 
Prof.  B.  Fink  of  Grinnell  was  also  examined  and  the  writer  made 
some  collections  in  Fremont  and  Ringgold  counties.  Unfortunately, 
a large  portion  of  the  collections  at  the  State  University  were  un- 
available at  the  time  of  the  writer's  visit  in  June,  1905. 

Synonyms  are  given  only  so  far  as  the  Iowa  literature  consulted 
is  concerned.  Following  the  name  of  the  host  plant  are  given  in 
their  order  the  locality,  time,  and  collector  of  specimens  on  that 
host.  If  any  of  these  items  are  lacking  its  place  is  taken  by  an  X. 
The  name  of  the  collector  is  in  parenthesis.  An  asterisk  (*)  indi- 
cates the  writer  has  not  seen  the  specimen  so  indicated  but  it  has 
been  reported  in  the  literature  consulted.  The  measurements  given 
in  the  descriptions  are  adopted  from  Salmon's  monograph  of  the 
family. 

ACKNOWLEDGMENTS. 

The  writer's  thanks  are  due  to  Prof.  B.  Fink  of  Grinnell  for  the 
privilege  of  examining  his  private  collection,  mostly  from  the  vi- 
cinity of  Fayette;  to  Profs.  Macbride  and  Shimek  for  courtesies 
extended  when  examining  the  collections  at  the  State  University; 
to  Prof.  Pammel  and  his  assistants  of  the  State  College  for  the 
privilege  of  examining  the  collections  at  Ames  and  assistance  ren- 
dered; to  Miss  King  of  the  botanical  department  at  Ames  who 
executed  most  of  the  drawings ; and  to  others  who  assisted  in  vari- 
ous ways.  Dr.  Macbride  has  given  much  valuable  information  in 
regard  to  Phyllactinia  corylea  tomentosa. 

LIST  OF  IOWA  WORKS  CONSULTED. 

Bessey,  C.  E. — The  Erysiphei.  Seventh  Bienniel  Rep.  Iowa  Agricultural 
College;  Preliminary  List  of  Carpophytes  of  the  Ames  Flora;  Bulletin,  Bot. 
Dept.  Iowa  Agri.  College,  Nov.,  1884. 

Fink,  B. — Blights,  Orchids  and  Ferns  of  Fayette,  Iowa.  Bull.  Upper  Iowa 
Uni.,  Jan.,  1894. 

Hitchcock,  A.  S. — Partial  list  of  Iowa  Powdery  Mildews.  Bulletin.  Iowa 
Agri.  College,  Nov.,  1886. 

Pammel,  L.  H. — Powdery  Mildew  of  the  Apple.  Cont.  Bot.  Dept.  Iowa  State 
College.  Iowa  Acad.  Sciences,  VII,  1899. 


8 


ERYSIPHACEAE,  Lev. 

Parasitic  on  living  plants.  For  further  description  see  introduction. 

KEY  TO  GENERA  OF  ERYSIPHACEAE. 

Ascus  Solitary — 

Appendages  of  perithecium  basal,  floccose,  similar  to  the  mycelium 

Sphaerotheca 

Appendages  of  perithecium  or  some  of  them  dichotomously  branched  at 


apex  Podosphaera 

Asci  Several — 

Appendages  of  perithecium  floccose,  similar  to  the  mycelium  and  frequently 

interwoven  with  it Erysiphe 

Appendages  of  perithecium  uncinate  or  coiled  at  apex Uncinula 

Appendages  of  perithecium  dichtomously  branched  at  apex Microsphaera 


Appendages  of  perithecium  rigid,  acicular,  with  a bulbous  base. . . .Phyllactinia 

SPHAEROTHECA,  Lev. 

Perithecia  subglobose,  ascus  solitary,  usually  containing  eight  spores.  Ap- 
pendages simple,  threads  resembling  the  mycelium  and  often  interwoven  with 
it,  rarely  obsolete. 


Key  to  Iowa  Species  of  Sphaerotheca. 

Mycelium  persistent,  thick  and  dense,  with  the  perithecia  more  or  less  im- 


mersed. 

Mycelium  white,  becoming  gray  or  pale  brown 3.  S.  pannosa 

Mycelium  becoming  dark  brown 4.  S.  mors-uvae 

Mycelium  evanescent,  subpersistent,  or  persistent,  not  thick  and  dense. 

Inner  wall  of  perithecium  separating  from  outer 5.  S.  phytoptophilg 

Inner  wall  of  perithecium  scarcely  separating. 

Cells  of  outer  wall  10-20  micra  wide 1.  S.  humuli 

Cells  of  outer  wall  20-30  micra  wide 2.  S.  humuli  fulginea 


1.  Sphaerotheca  humuli,  (DC.)  Burrill. 

Sphaerotheca  castagnei  Lev.  in  part.  Bessey,  The  Erysiphei  and  Prel.  List 
Ames  Flora.  Hitchcock,  Partial  List  Iowa  Powdery  Mildews.  Fink,  Blights, 
etc.,  of  Fayette. 

Sphaerotheca  pruinosa  C.  & P.  Bessey,  The  Erysiphei. 

Sphaerotheca  humuli  (DC.)  Burr.  Fink,  Blights,  etc.,  of  Fayette. 
Sphaerotheca  epilobi  (Lk.)  Sacc.  Fink,  in  E.  & E.  N.  A.  Fungi. 

Amphigenous;  mycelium  usually  evanescent,  sometimes  persistent,  forming 
white  spots  or  patches  on  the  upper  surface  of  the  leaf.  Perithecia  usually 
gregarious,  sometimes  scattered,  58-120  micra  in  diameter,  cells  small,  10-20 
micra  wide;  appendages  very  variable  as  to  length  and  color,  sometimes  even 
obsolete;  ascus  broadly  elliptical  to  subglobose,  45-90x50-72  micra,  spores  8, 
20-25-12-18  micra. 

On  Agrimonia  hirsuta  (Muhl.)  Bicknell,  Ames,  Oct.  15,  1878  (Bessey); 
Fayette.  (Fink). 


9 


On  Epilobium  coloratum  (Muhl.),  Ames,  Aug.  25,  1894  (Combs);  Fayette, 
Aug.  29,  1894  (Fink). 

On  Rhus  glabra  L.  Iowa  City,  X (X). 

On  Rosa  arkansana  Porter,  Ames,  1892  (Carver) ; Decatur  Co.,  Oct., 
1905  (Anderson). 

This  species  is  the  destructive  hop  mildew.  In  Europe  at  times 
great  losses  are  sustained  by  the  hop  grower  through  its  ravages. 
It  is  found  on  the  hop  in  some  parts  of  America  but  has  never  been 
reported  on  that  host  in  Iowa. 

2.  Sphaerotheca  humuli  fulginea  (Schlecht),  Salmon. 

Sphaerotheca  castaguei  Lev.  in  part.  Bessey,  The  Erysiphei,  and  Prel.  List 
Ames  Flora.  Fink,  Blights,  etc.,  of  Fayette.  Hitchcock.  Partial  list  Iowa 
Powdery  Mildews. 

As  in  S.  humuli  but  the  perithecia  usually  smaller,  wall  generally 
harder  and  more  brittle;  cells  larger  20-30  micra  or  more  wide; 
appendages  pale  to  dark  brown,  usually  short. 

On  Bidens  laevis  (L.),  B.  S.  P.  Ames,  Aug.  25,  1894  (Combs). 

On  Bidens  frondosa  L.,  Ames,  Aug.  22,  1877  (Bessey) ; Aug.  30,  1890 
(Brown) ; Aug.  25,  1894  (Combs) ; *Aug.,  1886  (Hitchcock) ; Decatur  Co., 
1904  and  1905  (Anderson);  Fayette,  Sept.,  1893  (Fink). 

On  Bidens  involUcrata  (Nutt),  Britton,  Decatur  Co.,  Oct.,  1905  (Anderson). 
On  Bidens  sp.,  Ames,  Oct.  1,  1892  (X). 

On  Erechitites  hieracifolia  (L.),  Raf.,  Ames,  Oct.  12,  1878  (Bessey);  De- 
catur Co.,  Oct.  10,  1904  (Anderson)  ; Johnson  Co.,  Sept.  16,  1899  (Shimek). 
On  Leptandra  virginica  (L.)  Nutt,  Ames,  Sept.  21,  1878  (Bessey)  ; Aug.  27, 
1892  (Carver) ; Decatur  Co.,  1904  and  1905  (Anderson)  ; Iowa  City,  Aug., 
1888  (Macbride) . 

On  Leptilon  canadense  (L.)  Britt.  *Fayette  (X),  (Fink). 

On  Prunella  vulgaris  L.  Ames,  Oct.  17,  1882  (Bessey). 

On  Sonchus  oleraceus,  L.  *Fayette  (Fink). 

On  Taraxacum  taraxacum  (L.),  Karst.  Ames,  Sept.  4,  1894  (Combs);  De- 
catur Co.,  Oct.,  1904  (Anderson) ; Iowa  City,  Oct.  18,  1886  (Macbride)  ; 
Oct.  3 (Bloom). 

The  variety  is  much  more  common  in  Iowa  than  the  type.  The 
type  of  the  species  is  seldom  collected  while  the  variety  is  very 
common.  Being  confined  to  weeds  it  works  no  injury  to  man  in 
Iowa. 

3.  Sphaerotheca  pannosa  (Wallr.),  Lev. 

Mycelium  abundant  on  the  stem  leaves,  petiole,  calyx,  etc.,  but  the  peri- 
thecia nearly  always  occurring  on  the  stem,  calyx  or  petiole,  white,  becoming 
gray  to  pale  brown.  Perithecia  more  or  less  immersed  in  the  dense  persistent 
mycelium,  globose  to  pyriform,  85-120  micra  in  diameter,  cells  about  10  micra 


10 


wide,  appendages  few,  sometimes  obsolete,  very  short,  tortuous,  pale  brown, 
septate.  Ascus  88-115x0-75  micra.  Spores  8,  20-27x12-15  micra. 

On  Rosa  blanda  Ait.  Fayette,  Aug.,  1894  (Fink). 

On  Rosa  sp.,  Decatur  Co.,  Nov.  18,  1905  (Anderson). 

This  species  has  been  much  confused  with  S.  humuli  and  S.  mors- 
uvae.  Bessey  and  Hitchcock  report  it  on  species  of  Ribes  but  S. 
mors-uvae  was  undoubtedly  the  species  intended.  S.  humuli  occurs 
on  the  leaves  of  roses.  S.  pannosa  in  its  conidial  stage  often  attacks 
the  entire  end  of  the  growing  shoot  of  Crimson  Rambler  roses  and 
thus  does  much  damage  to  this  variety  as  it  is  very  common  here 
in  Decatur  County.  I have  not  observed  it  as  destructive  to  other 
varieties.  I have  found  the  colored  mycelium  and  perithecia  only 
on  the  stems. 

4.  Sphaerotheca  mors-uvae  (Schwein),  Berk  and  Curt. 

See  Plate  II. 

Sphaerotheca  pannosa  Lev.  Bessey,  Prel.  List,  Ames  Flora;  Hitchcock,  Par- 
tial List  Iowa  Powdery  Mildews. 

Sphaerotheca  mors-uvae  (Schwein),  Berk  and  Curt.  Bessey,  The  Erysiphei, 
Fink,  Blight,  etc.,  of  Fayette. 

Mycelium  abundant,  at  first  white,  becoming  dark  brown;  forming  dense 
patches  on  the  fruit,  stem  and  leaves.  Perithecia  mostly  on  the  stem  and 
fruit,  gregarious,  immersed  in  the  persistent  mycelium,  76-100  micra  in 
diameter,  cells  10-25  micra  wide.  Appendages  few,  pale  brown,  short  and 
tortuous,  rarely  more  numerous  and  longer.  Ascus,  70-92x50-62  micra,  rarely 
longer.  Spores  20-25x12-15  micra.  , 

On  Ribes  cynosbati  L.  Ames,  July  3,  1876  (Bessey)  ; Fayette,  June  23  and 
29,  1894  (Fink). 

On  Ribes  gracile  Michx.  Ames,  July  2,  1896  (Carver) . 

On  Ribes  rotundifolium  Michx.  *Ames,  July,  1886  (Hitchcock) ; * Fayette 
(Fink) . 

On  Ribes  sp.  Ames  * (Bessey),  1894  (Carver);  Decatur  Co.,  June,  1904  and 
1905  (Anderson). 

This  species  is  easily  distinguished  from  all  others  by  the  dense, 
dark  brown,  felted  mycelium.  It  attacks  both  wild  and  cultivated 
species  of  Ribes  and  is  frequently  quite  injurious,  especially  to 
some  cultivated  varieties. 

5.  Sphaerotheca  phytoptophila,  Kellerm  & Swingle. 

Mycelium  evanescent  or  subpersistent,  perithecia  gregarious,  60-78  micra  in 
diameter,  cells  small,  about  10  micra  wide,  often  indistinguishable;  appendages 
short,  more  or  less  tortuous;  pale  to  dark  brown,  sometimes  obsolete  or  long, 
rarely  branched;  ascus  60-75x42-50  micra;  spores  8,  20-25x12-15  micra. 


11 


On  Celtis  accidentalis  L.,  on  the  distortions  caused  by  the  Phytoptus.  Ames, 
Jan.,  1889  (Halsted). 

This  was  distributed  as  No.  2336  of  Ellis  & Everhart’s  North  American 

Fungi. 

Podosphaera,  Kunze. 

Perithecia  globose  or  globose  depressed;  ascus  solitary;  spores  8.  Ap- 
pendages or  some  of  them  dichotomously  branched  at  the  apex.  In  P.  leuco- 
tricha  the  appendages  are  of  two  kinds. 

Key  to  Iowa  Species  of  Podosphaera. 

Appendages  of  one  kind 1.  P.  oxycanthae 

Appendages  of  two  kinds 2.  P.  leucotricha 

1.  Podosphaera  oxycanthae  (DC.),  DeBary. 

Podosphaera  kunzei  Lev.  Bessey,  The  Erysiphei. 

Podosphaera  minor  Howe,  Bessey,  The  Erysiphei. 

Podosphaera  tridactyla  DBy.  Bessey,  Prel.  List,  Ames  Flora.  Hitchcock,  Par- 
tial List  Iowa  Powdery  Mildews. 

Podosphaera  oxycanthae  (DC.),  DBy.  Fink,  Blights,  etc.,  of  Fayette. 

Amphigenous,  mycelium  variable,  persistent  or  evanescent;  perithecia  scat- 
tered or  gregarious  in  clinging  masses,  64-90  micra  in  diameter,  cells  10-18  micra 
wide;  appendages  4-30  in  number,  V2-6  times  the  diameter  of  the  perithecium, 
septate,  dark  brown  for  more  than  one-half  their  length,  apex  2-4  times 
dichotomously  branched,  branches  usually  short,  often  swollen,  tips  recurved; 
ascus  58-99x45-75  micra;  spores  18-30x10-17  micra. 

On  Crataegus  coccinea  L.  Ames,  X (X),  Iowa  City,  July  9,  1894  (Shimek). 
On  Crataegus  punctata  Jacq.  *Ames,  July,  1886  (Hitchcock) ; Iowa  City, 
Aug.,  1886  (Hitchcock). 

On  Crategus  tomentosa  L.  *Ames,  July,  1886  (Hitchcock) ; Iowa  City,  Oct. 
23,  1886  (Macbride) . 

On  Prunus  americana  Marsh.  Ames,  1891  (Raymond)  ; Sept.,  1890  (X) ; 

Decatur  Co.,  Oct.,  1904  (Anderson) . 

On  Prunus  avium  L.  Decatur  Co.,  Aug.  31,  1905  (Anderson). 

On  Prunus  besseyi  Bailey.  Decatur  Co.,  Oct.,  1904  (Anderson). 

On  Prunus  cerasus  L.  Ames,  Sept.  1,  1877  (Bessey),  1891  (Raymond),  Sept., 
1892  (Carver),  Aug.  20,  1894  (Sexton),  Sept.  13,  1894  (Stewart  & Stew- 
art), July  22,  1896  (Carver) ; Decatur  Co.,  Aug.,  1904  and  1905  (Anderson) ; 
Greenfield,  Sept.  13,  1893  (Stewart);  Iowa  City,  Oct.  1,  1886  (Macbride), 
1895  (Shimek). 

On  Prunus  pufnila  L.  Ames,  July  20,  1894  (Sexton),  Aug.  31,  1894  (Stewart 
& Stewart),  Oct.  19,  1892  (Carver). 

On  Prunus  sp.,  Ames,  Sept.  9,  1892  (Pammel) ; Fayette,  Sept.,  1893  (Fink) ; 
*Ames,  July,  1886  (Hitchcock). 

On  Sanguisorba  canandensis  L.  Forest  City,  July  17,  1896  (Shimek). 

This  is  a very  common  species,  especially  on  the  cultivated  cherry 
(Prunus  cerasus).  It  distorts  the  leaf  and  causes  premature  drop- 


12 


ping  thereby  greatly  weakening  the  vitality  of  the  tree.  On  Prunus 
cerasus  the  perithecia  usually  occur  on  the  under  side  of  the  leaf, 
while  on  the  other  hosts  they  are  often  found  on  the  upper  surface. 

2.  Podosphaera  leucotricha  (Ell.  & Ever.),  Salmon. 

Sphaerotheca  mali  Burr.  Fink,  Blights,  etc.,  of  Fayette.  Pammel,  Powdery 

Mildew  of  the  Apple,  Cont.  Bot.  Dept.  I.  S.  C.,  Iowa  Acad.  Sci.,  VII,  1899. 

Mycelium,  on  the  young  stem  petiole,  and  leaves,  persistent,  thin,  effused; 
perithecia  densely  gregarious,  rarely  scattered,  75-90  micra  in  diameter,  cells 
10-16  micra  wide;  appendages  of  two  kinds;  apical  appendages  3-11,  4-7  times 
the  diameter  of  the  perithecium,  becoming  thick  walled,  dark  brown  in  the 
lower  half,  paler  toward  the  tip,  apex  undivided  or  blunt,  rarely  once  or  twice 
dichotomously  forked;  basal  appendages  short,  tortuous,  pale  brown;  simple 
or  irregularly  branched;  ascus  55-70x44-50  micra;  spores  22-26x12-14  micra. 
On  Malus  malus  (L.)  Britt.  Ames,  *July,  1894  (Pammel)  ; Sept.  4,  1894 

(Combs);  Oct.,  1894  (Carver);  Fayette,  Oct.,  1893  (Fink). 

This  species  often  attacks  young  seedlings  in  the  nursery  and  at 
times  does  considerable  damage.  It  is  generally  classed  as  a Sphae- 
rotheca but  we  feel  inclined  to  agree  with  Mr.  Salmon  in  placing  it 
here.  The  appendages  certainly  show  characteristics  of  both  genera 
but  the  rigid  apical  appendages  are  certainly  very  unlike  the  ap- 
pendages in  Sphaerotheca.  The  occasional  forking  of  the  tips  of 
the  appendages  certainly  indicate  that  it  is  a Podosphaera. 

Erysiphe,  Hedw.  f. 

Perithecium  containing  several  asci,  each  ascus  2-8  spored;  appendages, 
threads  similar  to  the  mycelium  and  often  interwoven  with  it.  The  ap- 
pendages are  rarely  bosolete,  or  in  the  European  E.  tortilis,  brown,  assurgent 
and  fasciculate. 


Key  to  Iowa  Species  of  Erysiphe. 

Asci,  2-spored. 

Perithecia,  large,  135-240  micra  in  diameter,  becoming  pizzoid...5.  E.  taurica 
Perithecia,  80-140  micra  in  diameter. 

Haustoria  lobed 3.  E.  galeopsidis 

Haustoria,  not  lobed 2.  E.  cichoracearum 

Asci,  3-8  spored. 

Perithecia,  5-180  micra  in  diameter,  usually  about  90  micra 1.  E.  polygoni 

Perithecia,  130-280  micra  in  diameter,  usually  180-200  micra. . . .4.  E.  graminis 

Erysiphe  polygoni,  DC. 

See  Plate  III. 

Erysiphe  communis  (Wallr.),  Fr.  Bessey,  The  Erysiphei,  and  Prel.  List  Ames 
Flora.  Fink,  Blight,  etc.,  of  Fayette. 


13 


Erysiphe  martii  Lev.  Bessey,  the  Erysiphei,  and  Prel.  List  Ames  Flora. 

Hitchcock,  Partial  List  Iowa  Powdery  Mildews. 

Erysiphe  tortilis  (Wallr.),  Fr.  Bessey,  Prel.  List  Ames  Flora.  Hitchcock, 
Partial  List  Iowa  Powdery  Mildews. 

Amphigenous;  mycelium  variable,  thin,  effused  or  abundant,  persistent  or 
evanescent;  perithecia  gregarious  or  scattered,  5-180  micra,  usually  about  90 
micra  in  diameter,  cells  10-15  micra  wide;  appendages  very  variable  in  number 
and  length,  %-20  times  the  diameter  of  the  perithecium,  usually  interwoven 
with  the  mycelium,  colored  at  the  base  or  throughout  or  rarely  hyaline  or 
white;  asci  2-8,  rarely  mayn.  46-72x30-45  micra;  spores  3-8,  19-25x9-14  micra. 
On  Anemone  canadensis  L.  Iowa  City,  X (X). 

On  Anemone  sp.  Ames,  1894  (Carver). 

On  Anemone  virginiana  L.  Ames,  July  12,  1876  (Bessey). 

On  Astragalus  carolinianus  L.  Ames,  Sept.  9,  1894  (Combs) ; * Belle  Plaine, 
Sept.,  1886  (Hitchcock) ; Decatur  Co.,  Sept.,  1904,  and  Aug.  and  Sept., 
1905  (Anderson) ; Decorah,  Aug.  2,  1886  (Holway) ; Fayette,  Sept.,  1893 
(Fink). 

On  Brassica  nigra  (L.)  Koch.  Fremont  Co.,  Aug.  8,  1905  (Anderson). 

On  Clematis  virginiana  L.  Ames,  Oct.,  1882  (Bessey),  *Aug.,  1886  (Hitch- 
cock) ; Decatur  Co.,  Sept.,  1904  (Anderson) ; Iowa  City,  Oct.  10,  1886 
(Macbride),  Oct.  7,  1900  (Bloom).  Oct.,  1900  (Stromsten). 

On  Falcata  pitcheri  (T.  & G.),  Kunze,  Decatur  Co.,  Oct.,  1905  (Anderson). 
On  Geranium  maculatum  L.  Iowa  City,  Oct.  2 (Bloom). 

On  Onagra  biennis  (L.)  Scop.  Fayette,  1893  (Fink) ; Decorah,  Sept.  17,  1879 
(Holway) . 

On  Pisum  sativum  L.  Ames  X (X) ; Decatur  Co.,  June,  1905  (Anderson) ; 
Iowa  City,  May,  1886  (Macbride). 

On  Polygonum  aviculare  L,  Ames,  June  29,  1905  (Anderson)  ; Decatur  Co., 
July,  1904  and  1905  (Anderson). 

On  Polygonum  erectum  L.  Decatur  Co.,  July  12,  1905  (Anderson)  ; Ring- 
gold  Co.,  Oct.  7,  1905  (Anderson). 

On  Polygonum  ramosissimum,  Michx.  Fremont  Co.,  Aug.  8,  1905  (Ander- 
son). 

On  Ranunculus  abortivus  L.  Ames,  X (Rolfs)  ; Decatur  Co.,  July,  1904  and 
1905  (Anderson)  ; Iowa  City,  July,  1886  (Macbride). 

On  Syndesman  thalictroides  (L.),  Hoffman,  Iowa  City,  May,  1889  (Linder). 
On  Thalictrum  purpurascens  L.  Decatur  Co.,  July  12,  1905  (Anderson). 

This  is  the  most  variable  of  our  species  of  Erysiphaceae.  Were 
it  not  that  the  character  of  the  various  extreme  types  intergrade 
into  each  other  we  would  be  inclined  to  consider  various  types  as 
specifically  distinct.  Our  specimens  on  Polygonum  have  appendages 
only  I/2-II/2  times  the  diameter  of  the  perithecium  while  on  Clematis 
they  sometimes  reach  a length  of  15-20  times  the  diameter  of  the 
perithecium.  Other  Ranunculaceae  show  forms  with  appendages 
of  intermediate  length.  Other  characters  also  vary  widely.  In 
Decatur  County  Onagra  biennis  and  Syndesmon  thalictroides  are 


14 


affected  with  the  conidial  stage  but  I have  been  unable  to  find 
perithecia. 

The  cultivated  pea  (Pisum  sativum)  is  often  seriously  injured 
by  this  species.  The  other  Iowa  hosts  are  of  but  little  importance 
economically  with  the  exception  of  Clematis  which  is  sometimes 
cultivated  for  ornament.  During  the  seasons  of  1904  and  1905  one 
could  scarcely  find  a plant  of  Polygonum  erectum  but  what  was 
more  or  less  affected  and  thus  this  weed  was  largely  kept  in  check 
by  the  mildew. 

Erysiphe  cichoracearum,  DC. 

See  Plate  I. 

Erysiphe  cichoracearum,  DC.  Fink,  Blights,  etc.,  of  Fayette. 

Erysiphe  horridula,  Lev.  Bessey,  The  Erysiphei. 

Erysiphe  lamprocarpa,  Lev.  Bessey,  The  Erysiphei  and  Prel.  List  Ames  Flora; 
Hitchcock,  Partial  List  Iowa  Powdery  Mildews;  Halsted,  in  E.  & E.,  N.  A. 
Fungi  (424). 

Erysiphe  linkii  Lev.  * Halsted,  in  E.  & E.,  N.  A.  Fungi  (1904). 

Erysiphe  montagnei  Lev.  Bessey,  The  Erysiphei. 

Erysiphe  spadacea,  Berk  & Curt.  Bessey,  The  Erysiphei. 

Amphigenous;  mycelium  persistent  or  evanescent,  haustoria  not  lobed;  peri- 
thecia gregarious  or  scattered,  80-140  micra  in  diameter,  very  rarely  larger, 
cells  variable,  10-20  micra  wide;  appendages  variable,  generally  colored  and 
densely  interwoven  with  the  mycelium;  asci  4-25  or  more,  more  or  less  stalked, 
58-90x30-50  micra;  spores  quite  uniformly  2,  rarely  more,  20x28x12-20  micra. 

On  Ambrosia  artemisiae folia,  L.  Ames,  Sept.  1,  1894  (Combs)  ; Decatur  Co., 
Aug.  13,  1905  (Anderson)  ; *Fayette,  1894  (Fink)  ; Iowa  City,  Sept.  30, 
1886  (Macbride)  ; Oct.  6,  1893  (Bloom). 

On  Ambrosia  trifida,  L.  Ames,  Aug.  25,  1894  (Combs)  ; Sept.  5,  1873 
(Bessey)  ; *Aug.,  1886  (Hitchcock)  ; Decatur  Co.,  Aug.,  1904  and  1905 
(Anderson)  ; Fremont  Co.,  Aug.  8,  1905  (Anderson)  ; * Fayette,  1894 
(Fink)  ; Iowa  City,  Sept.  9,  1885  (Macbride)  ; Oct.  7,  1893  (Bloom) ; Ring- 
gold  Co.,  Oct.  7,  1905  (Anderson). 

On  Ambrosia  trifida  integrifolia  (Muhl.),  T.  & G.  Ames,  Sept.  22,  1894 
(Combs)  ; Decatur  Co.,  Sept.,  1905  (Anderson)  ; Ringgold  Co.,  Oct.  7,  1905 
(Anderson) . 

On  Ambrosia  psilostachya,  DC.  *Fayette,  1893  (Fink). 

On  Artemisia  biennis,  Willd.  Ames,  Sept.  22,  1894  (Combs). 

On  Artemisia  gnaphaloides,  Nutt.  Decorah,  Sept.,  1879  (Holway). 

On  Artemisia  serrata,  Nutt.  Ames,  Sept.,  1887  (Halsted). 

On  Aster  cordifolius,  L.,  Iowa  City,  Oct.  11,  1893  (Bloom). 

On  Aster  laevis  L.  Armstrong,  Sept.,  1895  (Shimek)  ; Decatur  Co.,  Sept., 
1904  and  1905  (Anderson) ; Fremont  Co.,  Aug.  7,  1905  (Anderson) ; Fay- 
ette, 1893  (Fink). 

On  Aster  sagittifolius,  Willd.  Ames,  Fall  1889  (X)  ; Fayette,  1893  (Fink) ; 
Muscatine,  Oct.  21,  1893  (Bloom). 


15 


On  Aster  salicifolius  Lam.  Ames,  Oct.  15,  1877  (Bessey). 

On  Aster  sp.  Ames,  Aug.  25,  1894,  and  Sept.  17,  1894  (Combs),  *Fayette, 
1893  (Fink). 

On  Carduus  altissimus,  L.  Ames,  Oct.  9,  1894  (Combs) ; Fayette,  Sept.,  1893 
(Fink);  Johnson  Co.,  Sept.  28,  1886  (Macbride). 

On  Carduus  discolor  (Muhl.),  Nutt.  Ames,  Sept.  12,  1894  (Combs),  Oct.  19, 

1892  (Carver)  ; Sept.  9,  X (Rolfs)  ; Decatur  Co.,  Oct.,  1905  (Anderson) ; 
Ringgold  Co.,  Oct.  7,  1905  (Anderson). 

On  Cosmos  bipinnatus.  'Ames,  Nov.,  1893  (Carver),  in  greenhouse. 

On  Eupfatorium  perfoliatum,  L.  Ames,  Sept.  19,  1892  (Carver). 

On  Eupatorium  purpureum  L.  Ames,  Sept.  17,  1892  (Carver). 

On  Galium  circaezans  Michx.  Decatur  Co.,  Sept.,  1904  and  1905  (Anderson). 
On  Helenium  autumnale,  L.  Ames,  Aug.  25,  1894  (Combs) ; Decatur  Co., 
Oct.,  1904  (Anderson)  ; Johnson  Co.,  Oct.  7,  1893  (Linder). 

On  Helianthus  annuus , L.  Ames,  Sept.  8,  1892  (Carver) ; * Fayette,  1893 
(Fink). 

On  Helianthus  doronicoides  Lam.  Ames,  Oct.  7,  1877  (Bessey). 

On  Helianthus  grosse-serratus  Martens.  Ames,  Sept.  15,  1894  (Combs)  ; De- 
catur Co.,  Sept.,  1904  (Anderson). 

On  Helianthus  sp.  Johnson  Co.,  X (X). 

On  Helianthus  tuberosus,  L.  Ames,  Sept.  22,  1894  (Combs)  ; Oct.  5,  1891 
(Rolfs)  ; Decatur  Co.,  Aug.,  1904  and  Sept.,  1905  (Anderson). 

On  Hydrophyllum  virginicum.  Ames,  Aug.  7,  1899  (Hume) ; Johnson  Co., 
May  25,  1894  (Glass). 

On  Lappula  virginica  (L)  Greene.  Johnson  Co.,  X (X). 

On  Leptilon  canadense  (L)  Britt.  Ames,  Sept.  22,  1894  (Combs). 

On  Parietaria  pennsylvanica,  Muhl.  Ames,  Aug.  19,  1899  (Hume  & Hodson). 
On  Phlox  divaricata  L.  Decatur  Co.,  July  12,  1905  (Anderson). 

On  Phlox  drummondii,  Hook.  Ames,  Oct.,  1892  (Bettinger) ; 1892  (Wright)  ; 
Fayette,  Sept.,  1893  (Fink). 

On  Phlox  procumbens.  Johnson  Co.,  May,  1889  (Linder). 

On  Plantago  major,  L.  Ames,  Oct.,  1901  (Lummis)  ; Decatur  Co.,  Oct.,  1904 
and  1905  (Anderson). 

On  Plantago  rugelii  Dec.  Decatur  Co.,  Oct.,  1904  (Anderson). 

On  Rudbeckia  hirta  L.  Johnson  Co.,  X (Macbride). 

On  Solidago  canandensis,  L.  Ames,  Sept.  22,  1894  (Combs)  ; * Fayette,  1893 
(Fink) . 

On  Solidago  rigida,  L.  *Fayette,  1893  (Fink). 

On  Solidago  serotina  Ait.  Iowa  City,  Oct.  3,  1893  (Bloom). 

On  Solidago  serotina  gigantea  (Ait.),  A.  Gray.  *Fayette,  1893  (Fink). 

On  Verbena  bracteosa,  Michx.  Ames,  1894  (Carver);  *Fayette,  1893  (Fink). 
On  Verbena  hastata,  L.  Ames,  Aug.  25,  1894  (Combs) ; Sept.,  1896  (Carver)  ; 
Decatur  Co.,  Aug.  3,  1905  (Anderson)  ; *Fayette,  1893  (Fink) ; Fremont 
Co.,  Aug.  8,  1905  (Anderson)  ; Des  Moines,  1895  (Carver) ; Iowa  City,  Oct., 
1895  (Macbride);  Aug.  25,  1893  (Bloom). 

On  Verbena  stricta,  Vent.  Ames,  Sept.  8,  1877  (Bessey) ; Aug.  25,  1893 
(Stewart)  ; Sept.  4,  1894  (Combs)  ; Oct.  7,  1901  (Paddock) ; June  28,  1905 
(Anderson) ; Fremont  Co.,  Aug.  8,  1905  (Anderson)  ; Greenfield,  Sept.  18, 

1893  (Stewart);  Johnson  Co.  X (X). 


16 


On  Verbena  urticifolia,  L.  Ames,  Aug.  30,  1894  (Combs) ; Oct.,  1890 
(Blaine) ; Oct.  19,  1877  (Bessey) ; 1894  (Carver)  ; Decatur  Co.,  Sept.  3, 
1905  (Anderson) ; *Fayette,  1893  (Fink) ; Decorah,  Oct.,  1879  (Holway) ; 
Iowa  City,  Oct.  3,  1893  (Bloom). 

On  Verbesina  alternifolia  (L.),  Britt.  Decatur  Co.,  Sept.,  1904  and  1905  (An- 
derson) . 

On  Vernonia  fasciculata,  Michx.  Ames,  Sept.  1,  1894  (Combs) ; Sept.  12,  1894 
(Stewart)  ; Iowa  City,  Oct.  7,  1893  (Linder). 

On  Vernonia  noveboracensis  (L),  Willd.  Polk  City,  Aug.  29,  1902  (Pammel) ; 
Johnson  Co.,  1889  (Linder). 

This  is  our  most  common  species  of  mildew,  and  behaves  some- 
what differently  on  the  different  host  plants.  On  Plantago  major 
the  mycelium  is  more  abundant  and  the  perithecia  more  numerous 
than  on  the  similar  but  thinner-leaved  P.  rugelii.  On  Aster  laevis 
I found  asci  with  2-4  spores  although  the  species  is  generally  easily 
recognized  by  its  numerous  2-spored  asci.  During  1904  I looked  in 
vain  for  perithecia  on  Verbena  hastata  and  V.  urticifolia,  but  found 
none  although  the  conidial  stage  was  very  abundant.  In  1905  I . 
found  an  abundance  of  perithecia  on  both  hosts.  I have  failed  to 
find  perithecia  on  a number  of  hosts  supposed  to  be  affected  with 
this  species  and  which  showed  conidia  in  abundance.  Of  the  host 
plants  here  reported  under  this  species  I have  found  the  conidial 
stage  on  the  following  in  Decatur  County  but  they  are  not  included 
in  the  preceding  data  because  no  perithecia  were  found.  Aster 
salicifolius,  A.  cordifolius,  Carduus  altissimus,  Hydrophyllum  vir- 
ginicum,  Lappula  virginica,  Solidago  canadensis,  Verbena  brac- 
teosa,  Vernonia  fasciculata,  V.  noveboracensis.  Although  so  com- 
mon this  species  is  not  important  economically.  Most  of  the  hosts 
attacked  are  weeds. 


3.  Erysiphe  galeopsidis  DC. 

Erysiphe  galeopsidis,  DC.  Fink,  Blights,  etc.,  of  Fayette. 

Closely  approaches  E.  cichoracearum,  but  is  distinguished  by  its  lobed 
haustoria  and  the  absence  of  spores  on  the  living  host  plant. 

On  Mint,  St.  Francis  river,  July  14,  1897  (X). 

On  Scutellaria  lateriflora,  L.  Ames,  Oct.  12,  1878  (Bessey)  ; Fayette,  1893 
(Fink);  Iowa  City,  Oct.  28,  1893  (Bloom). 

On  Scutellaria  galericulata  Ames,  1899  (Pammel). 

On  Stachys  palustris,  L.  Ames,  Oct.  5,  1898  (Ball). 

On  Stachys  sp.  Johnson  Co.,  X (X). 

On  Teucrium  canadense  L.  Johnson  Co.,  X (X). 

It  is  very  doubtful  if  this  form  is  entitled  to  rank  as  a distinct 
species.  It  has  been  ascertained  that  certain  forms  of  E.  cichora- 
cearum do  not  form  spores  on  the  living  host  plant  and  that  the 


17 


same  species  on  certain  hosts  shows  a tendency  to  form  lobed 
haustoria. 

4.  Erysiphe  graminis  DC. 

Erysiphe  graminis  DC.  Bessey,  Prel.  List  Ames  Flora;  Hitchcock;  partial 
list  Iowa  Powdery  Mildews;  Fink,  Blights,  etc.,  of  Fayette. 

Usually  epiphyllous;  mycelium  more  or  less  persistent;  perithecia  large, 
135-280  micra  in  diameter,  scattered  or  gregarious,  more  or  less  immersed  in  the 
persistent  mycelium,  cells  obscure;  appendages  rudimentary,  very  short,  pale 
brown;  asci  9-30,  pedicellate,  70-108x24-40  micra;  spores  8 (rarely  4)  ; 20-23x 
10-13  micra,  seldom  produced  on  the  living  host  plant. 

On  Cinna  arundinacea,  L.  Fayette,  1893  (Fink). 

On  Poa  pratensis , L.  *Ames,  Aug.,  1886  (Hitchcock)  ; Decatur  Co.,  Oct.  4, 
1904  (Anderson)  ; *Fayette,  1893  (Fink)  ; Johnson  Co.,  May  3,  1894  (X). 
This  species  is  quite  common  on  Poa  pratensis , but  the  perithecia  are  sel- 
dom found.  They  appear  to  be  formed  early. 

Erysiphe  taurica  Lev. 

Mycelium  often  covering  the  wjiole  plant,  usually  persistent,  effused,  dense- 
ly compacted,  tomentose,  membranaceous  or  crustaceous;  perithecia  usually  im- 
mersed in  the  persistent  mycelium,  large,  135-240  micra  in  diameter,  soon  be- 
coming concave;  cells  obscure;  appendages  usually  numerous,  densely  inter- 
woven, rather  short  and  vaguely  branched,  sometimes  very  short  or  even 
obsolete;  asci  7-38,  pedicellate,  large,  75-110x28-40  micra;  spores  2,  large, 
28-40x14-22  micra. 

On  Heliopsis  scabra  Dunal.  Decatur  Co.,  Aug.-Oct.,  1904  and  1905  (Ander- 
son) ; Ringgold  Co.,  Oct.  10,  1905  (Anderson). 

Heretofore  this  has  been  considered  as  an  old  world  species. 
Salmon,  in  his  monograph  of  the  Erysiphaceae,  gives  the  distribu- 
tion of  this  species  as  the  continent  of  Europe  (France,  Spain,  Italy, 
Greece,  Germany,  Austria-Hungary,  Russia),  Algeria  in  Africa, 
and  Turkey,  Syria,  Persia,  Turkestan,  and  India  in  Asia.  It  seems 
somewhat  strange  that  this  species  should  now  be  found  in  the 
middle  of  the  United  States,  but  I can  refer  the  form  under  consid- 
eration to  no  other  species  as  it  agrees  in  every  important  detail 
with  the  description  given  for  E.  taurica. 

In  August,  1904,  I first  collected  this  species  but  on  examination 
I found  that  the  perithecia  had  not  developed  asci.  I collected  at 
intervals  during  the  fall  but  not  until  very  late  in  the  season  could 
I find  traces  of  asci.  In  1905  I found  asci  somewhat  earlier  but 
have  been  unable  to  find  spores  without  soaking  in  water  for  24-48 
hours. 

During  the  autumns  of  1904  and  1905  nearly  every  plant  of 
Heliopsis  scabra  seen  by  the  writer  in  Decatur  and  Ringgold 
counties,  Iowa,  and  Harrison  County,  Missouri,  presented  a white 


18 


or  hoary  appearance,  from  the  presence  of  this  mildew.  It  had 
not  been  observed  previously  and  the  Heliopsis  scabra  seen  in  Fre- 
mont County  and  eastern  Nebraska  in  1905  was  not  affected. 

E.  M.  Freeman  in  Minnesota  Botanical  Studies  XXIV,  reports 
Erysiphe  cichoracearum  on  Heliopsis  scabra.  It  is  quite  probable 
that  this  was  the  species  under  consideration. 

Microsphaera  Lev. 

Perithecia  globose  to  globose  depressed;  asci  several,  2-8  spored;  append- 
ages free  from  the  mycelium ; more  or  less  dichotomously  branched  at  the  apex. 

Key  to  Iowa  Species  of  Microsphaera. 

Tips  of  appendages  recurved  when  mature. 

Appendages  short,  lA-2Vz  times  the  diameter  of  the  perithecium. . . .1.  M.  alni 
Appendages  long,  214-8  times  the  diameter  of  the  perithecium. 

Apex  much  branched,  ornate,  spores  22-26x12-15  micra. . . .3.  M.  alni  extensa 

Apex  less  branched,  spores  18-23x9-13  micra 2.  M.  alni  vaccinii 

Tips  of  appendages  not  recurved  when  mature. 

Appendages  colored ". 6.  M.  russellii 

Appendages  hyaline  or  nearly  so: 

Appendages  long,  2-7  times  the  diameter  of  the  perithecium,  contorted  and 

angularly  bent,  branching  irregular  and  lax 7.  M.  euphorbiae 

Appendages,  2-4  times  the  diameter  of  the  perithecium,  branching  lax 

5.  M.  diffusa 

Appendages,  1-2  times  the  diameter  of  the  perithecium,  branching  close  and 
regular 4.  M.  grossulariae 

Microsphaera  alni  (Wallr.)  Wint. 

Microsphaera  alni  (Wallr.),  Wint.  Fink,  Blights,  etc.,  of  Fayette. 
Microsphaera  abbreviata  Peck.  Bessey,  The  Erysiphei. 

Microsphaera  densissima  (Schwein.),  C.  & P.,  Bessey,  The  Erysiphei. 
Microsphaera  friesti  Lev.  Bessey,  Prel.  List  Ames  Flora;  Hitchcock,  Par- 
tial List  Iowa  Powdery  Mildews. 

Microsphaera  hedwigii  Lev.  Bessey,  The  Erysiphei;  Hitchcock,  Partial  List 
Iowa  Powdery  Mildews. 

Microsphaera  menispermi  E.  C.  Howe.  Bessey,  The  Erysiphei. 

Microsphaera  platani  E.  C.  Howe.  Bessey,  The  Erysiphei. 

Microsphaera  pulchra  Cook  & Peck.  Bessey,  The  Erysiphei. 

Microsphaera  ravenellii  Berk.  Bessey,  The  Erysiphei. 

Microsphaera  semitosta  Berk  & Curt.  Bessey,  The  Erysiphei. 

Microsphaera  quercina  (Schwein.),  Burr,  in  part.  Fink,  Blights,  etc.,  of  Fay- 
ette. 

Amphigenous;  mycelium  variable,  evanescent  or  persistent,  sometimes  form- 
ing definite  patches;  perithecia  scattered  or  gregarious,  66-110  micra  in  diameter, 
sometimes  larger;  cells  10-15  micra  wide;  appendages  4-26,  J4-214  times  the 
diameter  of  the  perithecium,  rigid,  sometimes  colored  at  the  base;  apex  various- 
ly but  closely,  3-6  times,  dichotomously  branched;  tips  recurved;  asci  3-8, 
42-70x32-50  micra;  spores,  4-8,  18-23x10-12  micra. 


19 


On  Alnus  rugosa  (Du  Roi),  K.  Koch,  Jones  Co.,  Aug.,  1895  (Macbride). 

On  Carpinus  caroliniantyi Walt.,  *Fayette,  1893  (Fink). 

On  Ceanothus  americanus  L.  Johnson  Co.  X (X). 

On  Cornus  candidissima  Marsh.  Muscatine,  Oct.  21,  1893  (Bloom). 

On  Corylus  americana  L.  Ames,  Sept.  2 and  14,  1878  (Bessey)  ; Sept.  8, 
1894  (Stewart  & Stewart);  Decatur  Co.,  Oct.,  1904  (Anderson);  *Fayette, 
1893  (Fink);  Johnson  Co.,  Sept.  29,  1886  (Macbride). 

On  Euonymons  autopur  purees  Jacq.  Fayette,  Sept.,  1893  (Fink). 

On  Flowering  pea.  Johnson  Co.,  Sept.,  1889  (Bloom). 

On  Juglans  regia.  Iowa  City,  Sept.,  1888  (Macbride). 

On  Lathyrus  odoratus  L.  Ames,  Oct.,  1902  (Fawcett) ; Johnson  Co.,  Aug., 

1892  (Macbride);  Corydon,  Nov.  6,  1900  (Stromsten). 

On  Lathyrus  palustris,  L.  Johnson  Co.,  X (X). 

On  Lofticera  sullivantii  A.  Gray.  Decorah,  Aug.,  1879  (Holway)  ; * Fayette, 

1893  (Fink);  Fremont  Co.,  Aug.  7,  1905  (Anderson). 

On  Lonicera  sp.  Ames,  Oct.  9,  1892  (Carver)  ; Forest  City,  X (X)  ; Decatur 
Co.,  Oct.,  1905  (Anderson). 

On  Menispermun  canadense  L.  *Holway  in  E.  & E..  N.  A.  Pyrenomycetes. 
On  Os'trya  virginiana  (Mill.),  Willd.,  Decatur  Co.,  Oct.  28,  1905  (Anderson). 
On  Quercus  macrocarpa  Michx.  Ames,  Oct.  9,  1894  (Combs.) 

On  Quercus  robur.  Ames,  Oct.,  1893  (Carver). 

On  Quercus  rubra  L.  Ames,  Sept.  14,  1878  (Bessey)  ; Oct.  20,  1882  (Osborn) ; 
Boone  Co.,  Aug.  19,  1903  (Pammel  & Buchanan)  ; Decatur  Co.,  Nov.,  1904 
(Anderson);  Iowa  City,  Sept.  9,  1900  (Shinnek) ; Oct.  7,  1898  (Bloom); 
Muscatine,  Oct.  20,  1900  (X). 

On  Quercus  velutina  Lam.  Johnson  Co.,  Oct.,  1886  (Macbride). 

On  Syringa  vulgaris  L.  Ames,  1878  (Bessey)  ; 1891  (Raymond) ; Oct.  9, 
1892  (Carver)  ; Sept.  4,  1894  (Coombs)  ; Sept.  10,  1894  (Stewart  & Stew- 
art) ; July  22,  1898  (Carver)  ; Oct.  14,  1901  (Lummis) ; Decatur  Co.,  Nov. 
7,  1905  (Anderson)  ; Fayette,  Sept.,  1893  (Fink)  ; Iowa  City,  Oct.  12,  1886 
(Macbride)  ; Jordan,  July  30,  1903  (Buchanan). 

On  Ulmus  americana  L.  *Fayette,  1893  (Fink). 

On  Vibernum  lentago  L.  Decorah,  Sept.  9,  1879  (Holway)  ; *Fayette,  1893 
(Fink)  ; Johnson  Co.,  X (X). 

On  Vida  sp.  Johnson  Co.,  Aug.  12,  1884  (Macbride). 

This  is  a common  and  very  variable  species  attacking  a great 
variety  of  host  plants.  In  the  State  University  herbarium  is  a 
specimen  on  Platanus  occidentalis  collected  in  October,  1901,  in 
Illinois  opposite  Muscatine.  This  species  does  not  appear  to  be  as 
destructive  as  some  others  but  injures  the  host  to  some  extent,  often 
quite  seriously. 

2.  Microsphaera  alni  vaccinii  (Schwein.)  Salmon. 

Microsphaera  elevata,  Burr.  Bessey,  The  Erysiphei;  Hitchcock,  Partial  List 
Iowa  Powdery  Mildews. 

Generally  epiphyllous;  mycelium  persistent  or  sometimes  evanescent;  peri- 
thecia  variable  in  size,  70-145  micra  in  diameter,  cells  10-20  micra  wide;  ap- 


20 


pendages  4-22,  2V2  -8  times  the  diameter  of  the  perithecium,  delicate,  hyaline 
or  occasionally  brown  at  the  base,  apex  2-4  times  dichotomously  branched, 
branches  variable;  tips  recurved;  asci  2-16,  45-72x28-38  micra,  spores  4-6, 
18-22x10-13  micra. 

On  Catalpa  catalpa  (L.),  Karst,  Johnson  Co.,  Sept.  25,  1886  (Macbride). 

On  Catalpa  speciosa  Warder.  Decatur  Co.,  1904  and  1905  (Anderson) ; *Iowa 
City,  Oct.,  1886  (Hitchcock);  Scott  Co.,  Sept.  1,  1897  (Macbride). 

This  species  is  occasionally  quite  destructive,  causing  a dying  and 
premature  dropping  of  the  leaves,  thereby  greatly  weakening  the 
tree. 

3.  Microsphaera  alni  extensa  (Cooke  & Peck)  Salmon. 

Microsphaera  extensa  Cooke  & Peck.  Bessey,  The  Erysiphei,  and  Prel.  List 
Ames  Flora;  Hitchcock,  Partial  List  Iowa  Powdery  Mildews. 

Microsphaera  quercina  (Schwein.),  Burr,  in  part.  Fink,  Blights,  etc.,  of  Fay- 
ette. 

Epiphyllous;  mycelium  persistent;  perithecia  gregarious,  90-140  micra  in 
diameter,  cells  10-20  micra  wide;  appendages  8-19,  21/£-6  times  the  diameter  of 
the  perithecium,  apex  3-5  times  dichotomously  forked;  tips  regularly  recurved; 
asci  3-8,  short  pedicellate,  58-72x34-45  micra;  spores,  4-8,  22-26x12-15  micra. 
On  Quercus  alba  L.  *Fayette,  1893  (Fink). 

On  Quercus  prinoides  Willd.  Decatur  Co.,  Oct.,  1904  (Anderson). 

On  Quercus  rubra  L.  *Fayette,  1893  (Fink). 

This  variety  seems  to  intergrade  with  the  type  of  the  species  and 
it  is  difficult  to  draw  the  line  between  them.  Some  of  the  specimens 
on  Quercus  referred  to  under  M.  alni  may  belong  here  and  the  two 
specimens  from  Fayette  referred  to  here  may  belong  under  M.  alni. 
Forms  on  Q.  rubra  from  Decatur  County  are  clearly  M.  alni  while 
specimens  on  Q.  prinoides  gathered  about  the  same  time  are  typical 
of  the  variety  extensa.  It  is  not  very  destructive. 

4.  Microsphaera  grossulariae  (Wallr.)  Lev. 

Microsphaera  grossulariae  (Wallr.),  Lev.  Bessey,  The  Erysiphei;  Fink, 
Blights,  etc.,  of  Fayette. 

Microsphaera  van  bruntae  Ger.  Bessey,  The  Erysiphei. 

Epiphyllous  or  amphigenous;  mycelium  evanescent  or  subpersistent,  peri- 
thecia scattered  to  densely  gregarious,  65-130  micra  in  diameter,  cells  14-20 
micra  wide;  appendages  5-22,  1-1%  times  the  diameter  of  the  perithecium, 
colorless,  apex  4-5  times  closely  dichotomously  branched,  ultimate  branches 
forming  a narrow  fork,  tips  not  recurved;  asci  4-10,  very  short  stalked,  46-62x 
28-38  micra;  spores  4-6;  very  rarely  only  3,  20-28x2-16  micra. 

On  Sambucus  canadensis  L.  Fayette,  Oct.,  1893  (Fink)  ; Johnson  Co.,  Oct., 
1889  (Linder). 

In  Europe  this  species  attacks  the  cultivated  gooseberry  and  is 
sometimes  quite  troublesome.  In  America  it  sometimes  attacks 


21 


other  species  of  Ribes  and  Sambucus.  The  American  gooseberry 
mildew  is  Sphaerotheca  mors-uvae.  M.  grossulariae  is  seemingly 

quite  rare  in  Iowa. 

5.  Microsphaera  diffusa , Cooke  & Peck. 

Microsphaera  diffusa  Cooke  & Peck.  Bessey,  The  Erysiphei. 

Microsphaera  symphoricarpi  E.  C.  Howe.  Bessey,  The  Erysiphei,  and  Prel. 
List,  Ames  Flora;  Hitchcock;  Partial  List  Iowa  Powdery  Mildews. 
Amphigenous;  mycelium  persistent  or  somewhat  evanescent;  perithecia  scat- 
tered or  gregarious,  variable,  55-126  micra  in  diameter,  cells  10-20  micra  wide; 
appendages  4-30  or  rarely  more,  W2-I  times  the  diameter  of  the  perithecium, 
colorless  or  pale  brown  toward  the  base  apex,  3-5  times  dichotomously  branched, 
tips  not  recurved,  branches  of  the  higher  orders  often  appearing  lateral;  asci 
4-9,  46-60x28-30  micra,  short  pedicellate;  spores  3-6,  18-22x9-11  micra. 

On  Meibomia  canadensis  (L.)  Kuntze.  Decatur  Co.,  Oct.,  1904  and  1905  (An- 
derson) ; Fremont  Co.,  Aug.  8,  1905  (Anderson)  ; Ringgold  Co.,  Oct.  7,  1905 
(Anderson) . 

On  Meibomia  sessilifolia  (Torr.),  Kuntze,  Ames,  Sept.  14,  1898. 

On  Symphoricarpos  symphoricarpos  (L.)  MacM.  Ames,  Sept.  7,  1882  (Bes- 
sey) ; Oct.  4,  1882  (Bessey)  ; Aug.,  1886  (Hitchcock)  ; Decatur  Co.,  Sept., 
1904  and  1905  (Anderson);  Corydon,  Nov.  5,  1900  (Stromsten);  Fremont 
Co.,  Aug.  7,  1905  (Anderson);  Johnson  Co.,  Oct.,  1882  (Hitchcock). 

The  form  on  Meibomia  has  generally  been  considered  distinct 
from  that  on  Symphoricarpos  but  there  does  not  appear  to  be  suffi- 
cient difference  to  justify  such  separation. 

In  the  southern  part  of  the  state  this  species  is  very  common  both 
on  Meibomia  canadensis  and  Symphoricarpos  vulgaris.  In  summer 
Symphoricarpos  sometimes  presents  a whitish  appearance  from  the 
abundance  of  the  conidial  stage  of  this  species. 

6.  Microsphaera  russellii  Clinton. 

Microsphaera  russellii  Clinton.  Bessey,  The  Erysiphei  and  Prel.  List  Ames 
Flora;  Hitchcock,  Partial  List  Iowa  Powdery  Mildews;  Fink,  Blights,  etc., 
of  Fayette. 

Amphigenous;  mycelium  inconspicuous;  perithecia  scattered,  70-118  micra  in 
diameter,  cells  6-14  micra  wide;  appendages  5-14,  3-7  times  the  diameter  of  the 
perithecium,  flaccid,  colored  nearly  to  the  apex,  septate,  apex  2-4  times 
dichotomously  branched,  branching  irregular  and  lax,  tips  not  recurved;  asci 
4-9,  short  pedicellate,  42-56x24-32  micra;  spores  3-5,  18-22x10-12  micra. 

On  Oxalis  stricta,  L.  Ames,  Oct.  17,  1878  (Bessey)  ; Decorah,  Oct.  19,  1878 
(Holway) ; Decatur  Co.,  Oct.,  1905  (Anderson) ; Fayette,  Oct.,  1892  (Fink) ; 
Iowa  City,  Oct.,  1886  (Hitchcock). 

^ In  this  species  the  appendages  are  very  slow  in  arriving  at  maturity. 

y,  Microsphaera  euphorbiae  (Peck),  Berk  & Curt. 

Erysiphe  euphorbiae  Peck.  Bessey,  The  Erysiphei. 

Microsphaera  euphorbia  (Peck),  Berk  & Curt.  Fink,  Blights,  etc.,  of  Fayette. 


22 


Amphigenous;  mycelium  subpersistent  or  sometimes  evanescent;  perithecia 
85-145  micra  in  diameter,  rarely  larger,  cells  10-15  micra  wide,  appendages  7-28, 
2^-8  times  the  diameter  of  the  perithecium,  flexuose,  often  angularly  bent, 
colorless,  aseptate,  apex  3-4  times  dichotomously  branched,  branching  irregu- 
lar and  lax,  tips  straight  or  recurved;  asci  4-13,  rarely  more;  short  pedicel- 
late, 48-66x26-33  micra;  spores  usually  4 (3-6),  19-21x10-12  micra. 

On  Euphorbia  corollata,  L.  Decatur  Co.,  Oct.,  1904  and  1905  (Anderson)  ; 
Decorah,  Sept.,  1879  (Holway)  ; * Fayette,  1893  (Fink) ; Ringgold  Co.,  Oct. 
7,  1905  (Anderson). 

On  Euphorbia  marginata  Pursh.  Johnson  Co.,  1888  (Macbride). 

As  in  some  other  species  of  Microsphaera  the  appendages  are 
very  slow  in  arriving  at  maturity,  hence  it  is  often  collected  with 
the  appendages  not  yet  branched. 

In  August,  1905,  I found  this  species  in  abundance  on  Euphorbia 
marginata  in  Cass  County,  Nebraska,  but  could  find  none  on  the 
east  side  of  the  Missouri  River  in  Fremont  County  although  the 
host  was  very  abundant. 

Uncinula  Lev. 

Perithecium  containing  several  asci,  asci  2-8  spored;  appendages  free  from 
the  mycelium,  uncinate  or  coiled  at  the  apex. 

Key  to  Iowa  Species  of  Uncinula. 

Appendages  colored 2.  U.  necator 

Appendages  hyaline  or  nearly  so. 

Asci -2  spored 5.  U.  macrospora 

Asci  4-8  spored. 

Appendages  delicate,  narrow,  3-4  micra  wide,  asci  4-7  spored. 

Appendages  50-160,  %-%  times  the  diameter  of  the  perithecium 

4.  U.  parvula 

Appendages  24-46,  l%-2  times  the  diameter  of  the  perithecium 


7.  U.  geniculata 

Appendages  stouter. 

Appendages  thick  walled,  refractive  at  base 6.  U.  clintoni 

Appendages  thin  walled. 

Asci  4-6  spored 1.  U.  salicis 

Asci  7-8  spored 3.  U.  circinata 


1.  Uncinula  salicis  (DC.)  Wint. 

Uncinula  adunca,  Lev.  Bessey,  The  Erysiphei,  and  Prel.  List,  Ames  Flora; 

Hitchcock,  Partial  List  Iowa  Powdery  Mildews. 

Uncinula  heliciformis  E.  C.  Howe.  Hitchcock,  Partial  List  Iowa  Powdery  Mil- 
dews. 

Uncinula  salicis  (DC.),  Wint.  Fink,  Blights,  etc.,  of  Fayette. 

Amphigenous;  mycelium  evanescent  or  persistent;  perithecia  90-175  micra  in 
diameter,  cells  10-15  micra  wide;  appendages  usually  numerous  or  crowded,  100- 


23 


150,  sometimes  less,  %- 2V2  times  the  diameter  of  the  perithecium,  simple, 
hyaline,  slightly  enlarged  upward;  asci  8-14,  rarely  less,  55-80x30-40  micra; 
spores  4-6,  20-26x10-15  micra. 

On  Populus  deltoides,  Marsh.  Johnson  Co„  X (X). 

On  Populus  grandidentata  Michx.  Columbus  Jc.,  Aug.,  1899  (Pammel)  ; John- 
son Co.,  X (Macbride). 

On  Populus  tremuloides,  Michx.  *Iowa  City,  Oct.,  1886  (Macbride). 

On  Salix  amygdaloides  Anders.,  Ames,  Aug.  30,  1894  (Combs). 

On  Salix  discolor , Muhl.  Ames,  Aug.  15,  1898  (Ball) ; Greenfield,  Sept.  18, 
1893  (Stewart);  Johnson  Co.,  Oct.  21,  1893  (Shimek). 

On  Salix  humilis,  Marsh.  Ames,  Sept.,  1899  (Pammel). 

On  Salix  sp.  Ames,  Oct.  12,  1878  (Bessey)  ; *July,  1886  (Hitchcock)  ; De- 
corah, Sept.,  1879  (Holway)  ; Fayette,  Sept.,  1893  (Fink)  ; Johnson  Co., 
Aug.,  1886  (Hitchcock)  ; Mason  City,  Sept.,  1900  (Shimek)  ; Rock  Rapids, 
Aug.  5,  1896  (Shimek). 

This  is  a very  variable  and  widely  distributed  species.  The  forms 
on  Populus  and  Salix  differ  somewhat  but  not  enough  to  justify 
separation. 

Uncinula  necator  (Schwein.)  Burr. 

Uncinula  americana,  E.  C.  Howe.  Bessey,  Prel.  List  Ames  Flora. 

Uncinula  ampelopsidis.  Peck.  Bessey,  Prel.  List  Ames  Flora,  Hitchcock,  Par- 
tial List  Iowa  Powdery  Mildews. 

Uncinula  necator  (Schwein.),  Burr.  Fink,  Blights,  etc.,  of  Fayette. 

Amphigenous,  with  perithecia  usually  epiphyllous,  sometimes  occurring  on 
the  inflorescence;  mycellium  evanescent  to  subpersistent ; perithecia  more  or 
less  scattered,  70-128  micra  in  diameter,  cells  rather  irregular  in  shape,  10-20 
micra  wide,  appendages  7-32,  1-4  times  the  diameter  of  the  perithecium,  septate, 
the  lower  half  colored ; apex  more  or  less  helicoid  when  mature ; asci  4-6,  rarely 
more,  50-60x30-40  micra;  spores  4-7,  18-25x10-12  micra. 

On  Parthenocissus  quinquefolia  (L),  Planch.  Ames,  Sept.  11,  1882  (Bessey); 
Aug.  17,  1899  (Hume) ; Decatur  Co.,  Sept,  and  Oct.,  1904  and  1905  (Ander- 
son) ; Decorah,  Sept.,  1879  (Holway)  ; Johnson  Co.,  Oct.  23,  1886  (Mac- 
bride); Ringgold  Co.,  Oct.  7,  1905  (Anderson). 

On  Vitis  cordifolia  Michx.  *Fayette,  1893  (Fink). 

On  Vitis  labrusca,  L.  Ames,  Aug.,  1891  (Pammel)  ; Oct.  30,  1891  (Rolfs)  ; 

Oct.,  1892  (Bettinger)  ; Decatur  Co.,  0.ct.,  1905  (Anderson). 

On  Vitis  sp.  Ames,  Sept.,  1889  (X)  ; Sept.,  1890  (Pammel)  ; Sept.  12,  1894 
(Combs)  ; Fayette,  Oct.,  1893  (Fink). 

This  is  the  powdery  mildew  of  the  grape  and  is  to  be  distinguished 
from  the  downy  mildew,  Peronospora  viticola.  In  Iowa  it  does  not 
appear  to  be  as  destructive  on  the  grape  as  it  is  on  the  Virginia 
creeper  (Parthenocissus  quinquefolia) . On  the  latter  host  it  is 
frequently  quite  destructive,  as  it  also  appears  to  be  on  the  grape 
in  some  regions.  In  Iowa  so  far  as  the  writer’s  observation  indi- 
cates, the  Peronospora  is  more  destructive  than  the  Uncinula. 


24 


Sulphur  and  Bordeaux  mixture  are  used  as  remedies  against  the 
present  species. 

. Uncinula  circinata  Cooke  & Peck. 

See  Plate  II. 

Uncinula  circinata,  Cooke  & Peck.  Bessey,  Prel.  List,  Ames  Flora;  Hitch- 
cock, Partial  List  Iowa  Powdery  Mildews;  Fink,  Blights,  etc.,  of  Fayette. 
Hypophyllous ; mycelium  usually  evanescent;  perithecia  usually  scattered, 
160-225  micra  in  diameter,  rarely  smaller;  cells  irregular,  10-14  micra  wide;  ap- 
pendages very  numerous,  usually  crowded,  their  length  rather  less  than  the 
diameter  of  the  perithecium,  simple,  hyaline,  apex  simply  uncinate;  asci  9-26, 
68-86x29-40  micra;  spores  8,  sometimes  only  7,  18-22x10-14  micra. 

On  Acer  saccharinum,  L.  Ames,  Oct.,  1894  (Carver)  ; * Belle  Plaine,  Sept., 
1886  (Hitchcock)  ; Decatur  Co.,  Oct.  28,  1905  (Anderson) ; Decorah,  Oct., 
1879  (Holway) ; Iowa  City,  Oct.  7,  1893  (Bloom). 

On  Acer  saccharum,  Marsh.  * Fayette,  Sept.,  1893  (Fink). 

A very  beautiful  species  under  the  microscope.  A specimen 
labeled  U . circinata  on  Acer  saccharum  in  Prof.  Fink's  herbarium 
proved  to  be  Phyllactinia  corylea. 

, ^Uncinula  parvula  Cooke  & Peck. 

Amphigenous;  mycelium  evanescent;  perithecia  usually  hypophyllous,  scat- 
tered, 86-122  micra  in  diameter,  cells  about  10  micra  wide;  appendages  nu- 
merous 50-160,  %-%  times  the  diameter  of  the  perithecium,  simple,  hyaline, 
apex  simply  uncinate;  asci,  5-8,  50-64x34-38  micra;  spores  4-7,  usually  6, 
20-24x10-12  micra.  On  Celtis  occidentalis  L.  Ames,  Sept.  15,  1878  (Bessey). 

Uncinula  macrospora  Peck. 

Uncinula  intermedia  Berk.  & Curt.  Bessey,  The  Erysiphei. 

Uncinula  macrospora  Peck.  Bessey,  The  Erysiphei;  Hitchcock,  Partial  List 
Iowa  Powdery  Mildews;  Fink,  Blights,  etc.,  of  Fayette. 

Amphigenous;  mycelium  evanescent  or  subpersistent,  often  forming  circum- 
scribed patches  on  the  upper  surface  of  the  leaf ; perithecia  gregarious  or  scat- 
tered, 95-165  micra  in  diameter;  cells  about  10  micra  wide;  appendages  50-130  or 
more,  'A-l  times  the  diameter  of  the  perithecium;  colorless;  aseptate;  apex 
simply  uncinate,  rarely  subhelicoid;  asci  8-14  or  more;  often  curved,  54-65x 
29-35  micra;  spores  2,  30x15-18  micra. 

On  Ulmus  americana  L.  *Cedar  Rapids,  Sept.,  1886  (Hitchcock) ; Decatur 
Co.,  Oct.,  1905  (Anderson)  ; Decorah,  Sept.,  1879  (Holway) ; Fayette,  Sept., 
1894  (Fink);  Johnson  Co.,  Sept.,  1885  (Macbride). 

On  Ulmus  racemosa  Thomas.  Decatur  Co.,  Oct.  28,  1905  (Anderson). 

On  Ulmus  americana  I have  found  the  perithecia  evenly  dis- 
tributed over  the  under  surface  of  the  leaf  with  the  mycelium  com- 
pletely evanescent  and  I have  also  found  it  with  mycelium  sub- 
persistent  in  circumscribed  patches  on  the  upper  surface  of  the  leaf. 


25 


On  Ulmus  racemosa  all  I have  found  has  been  in  circumscribed 
patches  on  the  upper  surface  of  the  leaf.  These  patches  are  often 
very  conspicuous. 

; 'Uncinula  clintoni  Peck. 

Uncinula  clintoni  Peck.  Hitchcock,  Partial  List  Iowa  Powdery  Mildews;  Fink, 
Blights,  etc.,  of  Fayette. 

Hypophyllous  or  amphigenous,  mycelium  usually  more  or  less  evanescent; 
perithecia  gregarious  or  scattered,  80-130  micra  in  diameter,  cells  irregular  in 
shape,  10-20  micra  wide;  appendages  10-35,  1-2^  times  the  diameter  of  the 
perithecium,  hyaline  or  somewhat  colored  at  base;  apex  clavate  uncinate;  asci 
4-10,  very  short  stalked,  40-62x34-40  micra;  spores  3-7,  20-27x10-13  micra. 

On  Tilia  americana  L.  Ames,  Sept.  22,  1878  (Bessey) ; 1878  (Thomas) ; 
Sept.,  1892  (Bettinger)  ; *Cedar  Rapids,  Sept.,  1886  (Hitchcock)  ; Decorah, 
Aug.,  1879  (Holway) ; *Fayette,  1893  (Fink)  ; Johnson  Co.,  Sept.  14,  1886 
(Macbride) ; Jones  Co.,  Aug.,  1895  (Macbride)  ; Muscatine,  Oct.  20,  1900 
(Stromsten). 

y,  Uncinula  geniculata  Gerard. 

Epiphyllous;  mycelium  thin;  forming  definite  patches  or  more  or  less  ef- 
fused, sometimes  evanescent;  perithecia  subgregarious  or  scattered,  90-120 
micra  in  diameter,  cells  rather  irregular,  10-15  micra  wide;  appendages  24-46, 
1*4-2  times  the  diameter  of  the  perithecium,  some  usually  abruptly  bent  or 
geniculate,  hyaline,  aseptate,  apex  simply  uncinate;  asci  5-8;  very  short  pedi- 
cellate, 48-56x34-38  micra;  spores  4-6,  22x12  micra. 

On  Morus  rubra  L.  Decatur  Co.,  Oct.  28,  1905  (Anderson). 

This  species  is  very  inconspicuous  and  may  be  much  more  common  than 
would  be  indicated  by  the  fact  that  it  is  not  often  collected. 

Phyllactinia  Lev. 

Perithecia  large;  asci  many;  2,  rarely  3-spored,  appendages  hyaline,  free 
from  the  mycelium,  acicular  or  rarely  flexuously  bent,  acute  at  tip  with  a 
bulbous  base;  apex  of  perithecium  provided  with  outgrowths  from  the  epider- 
mal cells.  This  genus  is  often  separated  from  the  others  as  a subfamily 
(Phyllactinicae) . This  distinction  is  based  on  the  fact  that  the  mycelium  does 
not  form  haustoria  in  the  ordinary  manner,  but  sends  special  branches  into 
the  stomata  of  the  host,  each  of  these  branches  giving  rise  to  an  haustorium 
which  penetrates  the  surrounding  tissue. 

Key  to  Iowa  Species  of  Phyllactinia. 

Appendages  undivided 1.  P.  corylea 

Appendages  divided  2.  P.  corylea  tomentosa 

Phyllactinia  corylea  (Pers.)  Karst. 

Phyllactinia  condollei  Lev.  Bessey,  The  Erysiphei. 

Phyllactinia  guttata  (Wallr.),  Lev.  Bessey,  The  Erysiphei. 

Phyllactinia  suffulta  (Rebent.),  Sacc.  Bessey,  Prel.  List.  Ames  Flora;  Hitch- 
cock, Partial  List  Iowa  Powdery  Mildews;  Fink,  Blights,  etc.,  of  Fayette. 


26 


Usually  hypophyllous;  mycelium  persistent  or  scant  and  evanescent;  perithe- 
cia  usually  scattered,  140-270  micra  in  diameter  or  larger,  cells  obscure,  15-20 
micra  wide;  appendages  5-18  or  more,  1-3  times  the  diameter  of  the  perithecium, 
acicular,  rigid,  hyaline,  aseptate,  swollen  at  the  base  into  a hollow  bulb,  asci 
5-45,  60-105x20-40  micra,  rarely  larger,  pedicellate,  spores  generally  2,  rarely 
3,  30-42x16-25  micra,  when  3 smaller. 

On  Acer  saccharum  Marsh.  Fayette  (Fink). 

On  Betula  papyrifera  Marsh.  *Fayette,  1893  (Fink). 

On  Cornus  fiorida  L.  *Fayette,  1893  (Fink). 

On  Cornus  stolonifera  Michx.  Fayette,  Sept.,  1893  (Fink). 

On  Corylus  americana,  L.  *Fayette,  1893  (Fink)  ; Johnson  Co.,  Sept.  25, 
1886  (Macbride) ; Sept.  19,  1899  (Shimek)  ; *Oct.,  1886  (Hitchcock). 

On  Crataegus  coccinea  L.  Johnson  Co.,  Oct.,  1894  (X). 

On  Crataegus  sp.  *Fayette,  1893  (Fink). 

On  Crataegus  tomentosa  L.  Ames,  Oct.  14,  1901. 

On  Celastrus  scandens  L.  Johnson  Co.,  X (X). 

On  Fraxinus  lanceolata  Berk.  Story  City,  Aug.  27,  1903  (Buchanan). 

On  Fraxinus  sp.  *Fayette,  1893  (Fink). 

On  Meibomia  canadense  (L.),  Kuntze.  Johnson  Co.,  X (X). 

On  Meibomia  grandiflora  (Walt.),  Kuntze.  *Fayette,  1893  (Fink). 

On  Ostrya  virginiana  (Mill.)  Willd.  Ames,  1877  (Bessey)  ; Decatur  Co.,  Oct. 
28,  1905  (Anderson)  ; Iowa  City,  Oct.  6,  1900  (Stromsten)  ; Muscatine,  Oct. 
20,  1900  (Stromsten). 

On  Quercus  palustris  DuRoi.  Jphnson  Co.,  Nov.,  1886  (Macbride). 

On  Quercus  rubra  L.  Johnson  Co.,  Oct.  12,  1886  (X). 

On  Quercus  velutina  Lam.  Johnson  Co.,  1886  (Macbride). 

On  Ulmus  americana  L.  *Fayette,  1893  (Fink). 

On  Ulmus  racemosa  Thomas.  Decatur  Co.,  Oct.  28,  1905  (Anderson). 

On  Xanthoxylum  americanum  Mill.  Ames,  Sept.  15,  1878  (Bessey) ; Fayette, 
Sept.,  1894  (Fink). 

This  species  seems  to  be  very  common  in  the  eastern  part  of  the 
state  but  is  not  so  plentiful  in  the  southwestern  part.  I have  found 
it  rarely  in  Decatur  County.  It  probably  does  not  grow  on  herba- 
ceous plants  but  perithecia  are  often  found  there.  The  apical  out- 
growths serve  to  attach  the  perithecium  to  the  substratum  and  by 
this  means  stray  perithecia  may  seem  to  be  firmly  attached  where 
they  did  not  originate. 

Phyllactinia  corylea  tomentosa,  Macbride  & Peck,  Var.,  Nov. 

See  Plate  I. 

Hypophyllous;  mycelium  persistent;  perithecia  as  in  P.  corylea;  appendages 
2-3  times  the  diameter  of  the  perithecium;  divided  down  to  the  bulbous  base, 
the  divisions  flexuously  bent  in  graceful  curves,  hyaline,  aseptate. 

On  Quercus  velutina,  Lam.  Johnson  Co.,  1886  (Macbride). 

In  the  herbarium  of  the  State  University  were  a few  specimens 
labeled  Phyllactinia  suffulta  var.  tomentosa.  On  inquiry  Prof. 


27 


Macbride  informed  the  writer  that  he  collected  the  same  during  the 
fall  of  1886  at  which  time  there  was  an  abundance.  It  covered  the 
entire  north  side  of  a tree  40  feet  high.  A quantity  was  collected 
but  most  of  it  was  afterward  found  missing.  No  special  effort  has 
since  been  made  to  collect  it. 

The  variety  is  based  on  the  appendages  which  are  markedly  dif- 
ferent from  those  of  the  type.  Profs.  Macbride  and  Peck  agreed 
upon  the  name  Phyllactinia  suffulta  tomentosa  for  the  variety.  It 
seems  that  corylea  rather  than  suffulta  is  the  name  that  should  be 
applied  to  the  species  and  is  so  published  here. 

The  occurrence  of  this  variety  and  the  circumstances  under  which 
it  was  found  are  rather  remarkable.  Its  taxonomic  position  is  a 
puzzle.  The  appendages  are  so  different  from  those  of  the  typical 
P.  corylea  that  it  might  be  considered  a distinct  species  if  it  could 
be  shown  that  these  differences  were  constant.  On  the  other  hand 
it  may  simply  be  a sport  due  to  some  peculiarities  of  host  plant  and 
season.  Several  facts  seem  to  lend  color  to  the  latter  view. 

HOST  INDEX. 

Abbreviations  used:  E.,  Erysiphe;  M.,  Microsphaera ; Ph.,  Phyllactinia; 


Po.,  Podosphaera;  S.,  Sphaerotheca ; U.,  Uncinula. 

For  those  marked  ? see  pages. 

Acer  saccharinum  L U.  circinata 

Acer  saccharinum  Wang.  See  A.  saccharinum  Marsh. 

Acer  saccharum  Marsh U.  circinata 

Acer  dasycarpum  Ehrh.  See  A.  saccharinum  L. 

Actinomeris  squarrosa  Nutt.  See  V erbesina  alternifolia. 

Adicea  pumila  (L.)  Raf E.  cichoracearum 

Agrimonia  eupatoria  L.  See  A.  hirsuta. 

Agrimonia  hirsuta  (Muhl.)  Bicknell S.  humuli 

Alnus  rugosa  (DuRoi)  K.  Koch M.  alni 

Alnus  serrulata  Willd.  See  A.  rugosa. 

Ambrosia  artemisiae folia  L E.  cichoracearum 

Ambrosia  psilostachya  DC E.  cichoracearum 

Ambrosia  trifida  L E.  cichoracearum 

Ambrosia  trifida  integrifolia  (Muhl.)  T.  & G E.  cichoracearum 

Ampelopsis  quinquefolia  Michx.  See  Parthenocissus  quinquefolia. 

Amphicarpa  pitcher i T.  & G.  See  Falcata  pitcheri. 

Anemone  canadensis  L E.  polygoni 

Anemone  pennsylvanica  L.  See  A.  canadensis. 

Anemone  sp E.  polygoni 

Anemone  virginiana  L E.  polygoni 

Anemonella  thalictroides  Spach.  See  Syndesmon  thalictroides. 

Artemisia  biennis  Willd E.  cichoracearum 

Artemisia  gnaphaloides  Nutt E.  cichoracearum 

Artemisia  serrata-  Nutt E.  cichoracearum 


28 


Asclepias  tuberosa  L ? 

Astragalus  carolinianus  L E.  polygoni 

Astragalus  canadensis  L.  See  A.  carolinianus. 

Aster  carneus  T.  & G.  See  A.  salicifolius. 

Aster  cordifolius  L E.  cichoracearum 

Aster  laevis  L E.  cichoracearum 

Aster  multiflorus  Ait ? 

Aster  purpuratus  Nees E . cichoracearum 

Aster  sagittifolius  Willd E.  cichoracearum 

Aster  salicifolius  Lam E.  cichoracearum 

Betula  papyrifera  Marsh Ph.  corylea 

Bidens  laevis  (L.)  B.  S.  P S.  humuli  fulginea 

Bidens  frondosa  L S.  humuli  fulginea 

Bidens  involucrata  (Nutt.)  Britton S.  humuli  fulginea 

Bidens  sp S.  humuli  fulginea 

Brassica  nigra  (L.)  Koch E.  polygoni 

Brassica  sp  ? 

Brunella  vulgaris.  See  Prunella  vulgaris. 

Cacalia  tuberosa  Nutt.  See  Prunella -vulgaris. 

Carduus  altissimus  L E.  cichoracearum 

Carduus  discolor  (Muhl.)  Nutt E.  cichoracearum 

Carpinus  caroliniana  Walt M.  alni 

Catalpa  bignonoides  Walt.  See  C.  catalpa. 

Catalpa  catalpa  (L.)  Karst M.  alni  vaccinii 

Catalpa  speciosa  Warder M.  alni  vaccinii 

Ceanothus  americanus  L M.  alni 

Celastrus  scandens  L Ph.  corylea 

Celtis  occidentalis  L S.  phytoptophila — U.  parvula 

Cinna  arundinacea  L E.  graminis 

Chrysanthemum  sp  ? 

Clematis  virginiana  L E.  polygoni 

Cnicus  altissimus  Willd.  See  Carduus  altissimus. 

Cnicus  altissimus  discolor  A.  Gray.  See  carduus  discolor. 

Cnicus  discolor  Muhl.  See  carduus  discolor. 

Coreopsis  involucrata  Nutt.  See  Bidens  involucrata. 

Cornus  florida  L Ph.  corylea 

Cornus  candidissima  Marsh M.  alni 

Cornus  stolonifera  Michx Ph.  corylea 

Cornus  paniculata  L’Her.  See  C.  candidissima. 

Corylus  americana  L :M.  alni — Ph.  corylea 

Cosmos  bipinnatus  E.  cichoracearum 

Crataegus  coccinea  L Po.  oxycanthae — Ph.  corylea 

Crataegus  punctata  Jacq Po.  oxycanthae 

Crataegus  sp Po.  oxycanthae — Ph.  corylea 

Crataegus  tomentosa  L Po.  oxycanthae— Ph.  corylea 

Cucumis  sativa  L ? 

Diospyros  virginiana  L 

Desmodium  canadense  DC.  See  Meibomia  canadensis. 

Desmodium  acuminatum  DC.  See  Meibomia  grandiflora. 


29 


Desmodium  sessilifolium  T.  & G.  See  Meibomia  sessilifolia. 

Echinospermum  virginicum  Lehm.  See  Lappula  virginica. 

Epilobium  coloratum  Muhl S.  humuli 

Erechitites  hieracifolia  (L.)  Raf S.  humuli  fulginea 

Erigeron  canadensis  L.  See  Leptilon  canadense. 

Euonymous  atropurpureus  Jacq M.  alni 

Eupatorium  perfoliatum  L E.  cichoracearum 

Eupatorium  purpureum  L E.  cichoracearum 

Euphorbia  carollata  L M.  euphorbiae 

Euphorbia  marginata  Pursh M.  euphorbiae 

Falcata  pitcheri  (T.  & G.)  Kuntze E.  polygoni 

Fraxinus  lanceolata  Berk Ph.  corylea 

Fraxinus  sp  Ph.  corylea 

Fraxinus  viridis  Michx.  See  F.  lanceolata. 

Flowering  pea M.  alni 

Galium  circaezans  Michx E.  cichoracearum 

Geranium  maculatum  L E.  polygoni 

Grindelia  squarrosa  (Pursh)  Dunal.  . . .. ? 

Geum  virginicum  L .? 

Helenium  autumnale  L E.  cichoracearum 

Helianthus  annuus  L E.  cichoracearum 

Helianthus  doronicoides  Lam E.  cichoracearum 

Helianthus  grosse-serratus  Martens E.  cichoracearum 

Helianthus  sp E.  cichoracearum 

Helianthus  tuberosus  L E.  cichoracearum 

Heliopsis  scabra  Dunal E.  taurica 

Hydrophyllum  virginicum  E.  cichoracearum 

Juglans  regia M.  alni 

Lactuca  canadensis  L ? 

Lactuca  floridana  (L)  Gaertn ? 

Lactuca  sagittifolia  Ell ? 

Lappula  virginiana  (L.)  Greene E.  cichoracearum 

Lathyrus  odoratus  L M.  alni 

Lathyrus  palustris  L M.  alni 

Leptandra  virginica  (L.)  Nutt S.  humuli  fulginea 

Leptilon  canadense  (L.)  Britton S.  humuli  fulginea — E.  cichoracearum 

Lonicera  sp  M.  alni 

Lonicera  sullivantii  A.  Gray M.  alni 

Malus  malus  (L.)  Britton Po.  leucotricha 

Meibomia  canadensis  (L.)  Kuntze M.  diffusa — Ph.  corylea 

Meibomia  grandiflora  (Walt.)  Kuntze Ph.  corylea 

Meibomia  sessilifolia  (Torr.)  Kuntze M.  diffusa 

Menispermum  canadense  L M.  alni 

Mesadenia  tuberosa  (Nutt.)  Britton ? 

Mint E.  galeopsidis 

Monarda  fistulosa  L ? 

Morus  rubra  L U.  geniculata 

Nasturtium  sylvestre,  R.  Br.  See  Roripa  sylvestris. 

Oenothera  biennis  L.  See  Onagra  biennis. 


30 


Onagra  biennis  (L.)  Scop...,, E.  polygoni 

Ostrya  virginiana  (Mill.)  Willd M.  alni — Ph.  corylea 

Oxalis  stricta  L M.  russellii 

Parietaria  pennsylvanica  Muhl E.  cichoracearum 

Parthenocissus  quinquefolia  (L.)  Planch U.  necator 

Phlox  divaricata  L E.  cichoracearum 

Phlox  drummondii  Hook E.  cichoracearum 

Phlox  procumbens E.  cichoracearum 

Phlox  sp  ? 

Pilea  pumila  A.  Gray.  See  Adicea  pumila. 

Physostegia  virginiana  (L.)  Beuth ? 

Physalis  heterophylla  Nees E.  polygoni 

Plantago  major  L f E.  cichoracearum 

Plantago  rugelii  Dec E.  cichoracearum 

Platanus  occidentalis  L M.  alni 

Poa  pratensis  L E.  graminis 

Polygonum  aviculare  L E.  polygoni 

Polygonum  erectum  L E.  polygoni 

Polygonum  ramosissimum  Michx E.  polygoni 

Populus  deltoides  Marsh U.  salicis 

Populus  grandidentata  Michx U.  salicis 

Populus  monilifera  Ait.  See  P.  deltoides. 

Populus  tremuloides  Michx U.  salicis 

Potentilla  monspeliensis  L ? 

Potentilla  norvegica  L.  See  P.  monspeliensis. 

Poterium  canadense  A.  Gray.  See  Sanguisorba  canadensis. 

Prunella  vulgaris  L S.  humuli  fulginea 

Prunus  americana  Marsh Po.  oxycanthae 

Prunus  avium  L Po.  oxycanthae 

Prunus  besseyi  Baily Po.  oxycanthae 

Prunus  cerasus  L Po.  oxycanthae 

Prunus  pumila  L Po.  oxycanthae 

Prunus  sp  Po.  oxycanthae 

Pyrus  malus  L.  See  Malus.  malus. 

Quercus  alba  L M.  alni  extensa 

Quercus  macrocarpa  Michx M.  alni 

Quercus  palustris  DuRoi M.  alni — Ph.  corylea 

Quercus  prinoides  Willd M.  alni  extensa 

Quercus  robur  M.  alni 

Quercus  rubra  L M.  alni — M.  alni  extensa — Ph.  corylea 

Quercus  velutina  Lam M.  alni — Ph.  corylea — Ph.  corylea  tomentosa 

Ranunculus  abortivus  L E.  polygoni 

Rhus  glabra  L S.  humuli 

Ribes  cynosbati  L S.  mors-uvae 

Ribes  gracile  Michx S.  mors-uvae 

Ribes  sp S.  mors-uvae 

Ribes  rotundifolium  Michx.? <S.  mors-uvae 

Ribes  sp S.  mors-uvae 

Roripa  sylvestris  (L.)  Bess 


Rosa  arkansana  Porter S.  humuli 

Rosa  blanda  Ait? S.  pannosa 

Rosa  sp  S.  pannosa 

Rudbeckia  hirta  L E.  cichoracearum 

Rudbeckia  laciniata  L ? 

Rudbeckia  triloba  L ? 

Salix  amygdaloides  Anders U.  salicis 

Salix  discolor  Muhl U.  salicis 

Salix  humilis  Marsh U.  salicis 

Salix  sp U.  salicis 

Sambucus  canadensis  L M.  grossulariae 

Sanguisorba  canadensis  L Po.  oxycanthae 

Scutellaria  lateriflora  L E.  galeopsidis 

Scutellaria  galericulata  E.  galeopsidis 

Sisymbrium  officinale  Scop ? 

Solanum  carolinense  L ? 

Solidago  canadensis  L E.  cichoracearum 

Solidago  rigida  L E.  cichoracearum 

Solidago  serotina  Ait E.  cichoracearum 

Solidago  serotina  gigantea  (Ait.)  A.  Gray E.  cichoracearum 

Solidago  ulmifolia  ? 

Sonchus  oleraceus  L S.  humuli  fuliginea 

Stachys  palustris  L E.  galeopsidis 

Stachys  sp E.  galeopsidis 

Symphoricarpos  symphoricarpos  (L.)  MacM M.  diffusa 

Symphoricarpos  vulgaris  Michx.  See  S.  symphoricarpos. 

Syndesmon  thalictroides  (L.)  Hoffing E.  polygon* 

Syringa  vulgaris  L M.  alni 

Taraxacum  officinale  Weber.  See  F.  taraxacum. 

Taraxacum  taraxacum  (L.)  Karst <S.  humuli  fulginea 

Taraxacum  canadense  L E.  galeopsidis 

Thalictrum  purpurascens  L E.  polygoni 

Tilia  americana  L U.  clintoni 

Ulmus  americana  L M.  alni — U.  macrospora — Ph.  corylea 

Ulmus  racemosa  Thomas U.  macrospora — Ph.  corylea 

Verbena  bracteosa  Michx E.  cichoracearum 

Verbena  hastata  L E.  cichoracearum 

Verbena  stricta  Vent E.  cichoracearum 

Verbena  urtici folia  L E.  cichoracearum 

Verbesina  alternifolia  (L.)  Britton E.  cichoracearum 

Veronica  virginica  L.  See  Leptandra  virginica. 

Vernonia  fasciculata  Michx E.  cichoracearum 

Vernonia  noveboracensis  (L.)  Willd E.  cichoracearum 

Viburnum  lentago  L * M.  alni 

Vida  sp M.  alni 

Vitis  cordifolia  Michx U.  necator 

Vitis  labrusca  L U.  necator 

Vitis  sp U.  necator 

Xanthium  canadense  Mill ? 

Xanthoxylum  americanum  Mill Ph.  corylea 


32 


Index  to  Species  and  Varieties  of  Erysiphaceae. 


Recognized  species  are  in  italics;  synonyms  are  in  Roman. 


Erysiphe  24  Phyllactinia  

cichoracearum  26  corylea  , 

cummunis  24  corylea  tomentosa 

galeopsidis  28  guttata  

graminis  29  suffulta  

horidula  26  Podosphaera 

lamprocarpa  26  kunzei  

linkii  26  leucotricka  

martii  25  minor  

montagueii  26  oxycanthae  

polygoni  24  tridactyla  

spadacea  26  Sphaerotheca  

tauraica  29  castagnei  

tortilis  25  epilobi  

Microsphaera I ft..-.  ~ 30  humuli 

abbreviata  30  humuli  fulginea  . . 

alni  30  mors-uvae  

alni  extensa  32  pannosa  

alni  vaccinii 31  phytoptophila  . . . 

densissima  30  pruinosa  

diffusa  33  Uncinula 

elevata  31  adunca 

euphorbiae  33  americana 

extensa  32  ampelopsidis 

friesii  30  circinata  

grossulariae  32  clintoni  

hedwigii  30  geniculata 

menispermi 30  heliciformis  

platani  30  intermedia  

pulchra  30  macrospora 

quercina  30-32  necator  

raven elii  30  parvula  

russellii  33  salicis  

semitosta 30  spiralis  

symphoricarpi  33 


37 

37 

38 

§7 

37 

..fall-  13 

23 

,24 

23 

23 

23 

. . . XrJO  Id 

20-21 

20 

20 

21 

22 

21-22 

22 

20 

..ZLA'Jfi  4 

34 

35 

35 

36 

37 

37 

34 

36 

36 

35 

36 

34 


33 


EXPLANATION  OF  PLATES. 


PLATE  I. 

Fig.  1.  Phyllactinia  corylea  tomentosa.  a and  b,  two  appendages;  c,  an 
appendage  of  the  typical  P.  corylea  from  same  leaf  as  a and  b.  (Author’s 
illustration.) 

Fig.  2.  Hyphae  and  conidia  of  Erysiphe  cichoracearum , from  leaf  of  Hydro- 
phyllum  virginicum.  (Drawn  by  Miss  King.) 

Fig.  3.  A fruit  of  Ampelomyces  quisqualis.  a.  A mycelium  of  Erysiphe 
with  the  fruit  of  Ampelomyces;  b,  arising  out  of  it;  c,  spores  escaping  from 
the  ruptured  end  of  fruit.  (Author’s  illustration.) 

PLATE  II. 

(Drawn  by  Miss  King.) 

(See  page  46.) 

Fig.  1.  A perithecium  of  Uncinula  circinata  from  a leaf  of  Acer  sacchar- 
inum  showing  very  numerous  appendages  uniformly  coiled  at  apex. 

Fig.  2.  Perithecia  of  Sphaerotheca  mors-uvae  from  the  cultivated  goose- 
berry, showing  few  or  obsolete  appendages  and  the  persistent  mycelium  in 
which  they  are  immersed. 

PLATE  III. 

(See  page  46.) 

Showing  Variations  in  Erysiphe  polygoni.  (Drawn  by  Miss  King.) 

Fig.  1.  From  a leaf  of  Clematis  virginiana,  showing  few,  but  long  flexuose 
appendages. 

Fig.  2.  From  a leaf  of  Astragalus  carolinianus,  showing  more  numerous 
but  short  appendages,  b.  Tips  of  appendages. 


34 


PLATE  III. 


